Image source, EPA

Welcome back to our live coverage of the Iowa caucuses, which should have all been over by now.

Here's where we are:

• Results were due on Monday night but the count descended into chaos as the app used to report results crashed and the phone lines were jammed
• Iowa's state Democratic Party initially said there was a reporting issue, later adding that there had been a coding error in the app
• The Democratic Party has said more than 50% of results will be released at 16:00 local time (22:00 GMT) on Tuesday.
• Candidates expressed frustration at the process. Both Bernie Sanders and Pete Buttigieg suggested they were ahead, based on internal campaign data, while Joe Biden's team attacked the integrity of the results
• Democrats said the integrity of the results had not been compromised, they had only been slowed by the technical glitches
• President Donald Trump described the caucuses as "an unmitigated disaster"

Iowa Democratic Party Chairman Troy Price has just said party officials expect to report results from the caucuses “later” on Tuesday. He explained they were validating data against paper records and verifying all precinct results, a process that was “taking longer than expected”.

Mr Price was reading a statement while on a call with reporters. He said the delay was not a result of a hack or an intrusion.

With that news in mind, we're pausing our live coverage for now. You can follow the latest developments in our main news story - and we'll be back with live reporting and analysis as soon as those results come through.

It was a chaotic night - and it continues to be so - in Iowa. Here's the story of what has happened so far.

In the absence of official results, the candidates are starting to put out their own versions of events. Bernie Sanders is claiming victory, citing internal campaign data that places him ahead of Pete Buttigieg.

The data released by the Sanders campaign, which said it represented results from nearly 40% of precincts in Iowa, showed the senator garnering 28.62% of the vote, followed by Mr Buttigieg on 25.71%.

"We recognise that this does not replace the full data from the Iowa Democratic Party, but we believe firmly that our supporters worked too hard for too long to have the results of that work delayed," his adviser, Jeff Weaver, said.

A little earlier (see 05:32) Mr Buttigieg was on stage himself, telling supporters that "by all indications we are going on to New Hampshire victorious" - although he didn't cite any evidence to back the claim.

As it passes midnight in Iowa, 01:00 here in Washington DC, and 06:00 in London, here's where things stand.

We were expecting to bring you the results from the Iowa caucuses, the first big step towards deciding which Democrat will take on Trump in November's presidential election. It didn't work out that way.

Here's what we know:

• There have been significant delays in announcing the results
• The Iowa Democratic Party says the delay is due simply to "a reporting issue", and not a hack
• However, the BBC has been told there were serious issues state-wide with a reporting app - some officials had to phone in results instead
• It is still unclear when results will be announced
• Joe Biden, one of the favourites in Iowa, is the first candidate to condemn the delay, saying there were "considerable flaws" with the reporting system

Thanks for reading - here's our latest news story on Iowa, that we'll keep updating over the next few hours.

Joe Biden's campaign has written to the Iowa Democratic Party (IDP) slamming the "considerable flaws in tonight's Iowa Caucus reporting system" and requesting "an opportunity to respond before any official results are released".

The results reporting app "failed" and the party's "back-up telephonic reporting system likewise failed".

"These acute failures are occurring statewide," their letter says.

"The campaigns deserve full explanation and relevant information regarding the methods of quality control you are employing."

Our teams in Iowa are still waiting for the numbers to come in, indicating which candidates performed best heading into the New Hampshire primary next week.

Remember that Tuesday night sees the prime-time State of the Union speech, that is delivered each year by the president.

Many political junkies who have flown to Iowa, including many of our own staff, have no choice but to rush back to Capitol Hill in just a few hours' time.

Pete Buttigieg took to the stage just before 23:30 local time to address his supporters.

"What a night, because tonight an improbable hope became an undeniable reality," he said to cheers, taking perhaps the most triumphant tone of all other candidates to speak this evening - even in the absence of reported results.

"We don't know all the results but, we know, Iowa you have shocked the nation, because by all indications we are going on to New Hampshire victorious," he said.

Buttigieg may know something we don't, or may be talking up his chances - there were indications that he was doing well, but not that he had beaten Sanders and Biden.

Marianna Brady
BBC News, Des Moines

This is your first caucus – who do you support?

I am a Bernie Sanders supporter. I was choosing between Bernie and Warren but then realised they weren’t the same policy-wise. On healthcare and climate, Bernie is more progressive.

A lot of my friends are in between Bernie and Warren. One is a Pete [Buttigieg] supporter.

Why Bernie Sanders?

Bernie is the best person for young people – it’s incredible to see how many young people support him.

Because he’s so old there’s a sense of authenticity that comes with him wanting a revolution – because it’s not for him. It’s out of a pureness of his heart.

He has a drive to want to make the country better. It feels selfless and not political. I think the younger generation see the problems that this country faces as more of a graver danger than older generations – we’re less jaded and less willing to accept that the status quo. That’s why Bernie speaks to us.

If Bernie isn’t viable, who would you support?

Elizabeth Warren is definitely my second option – that’s an easy second. My third is Pete Buttigieg because he’s the next most progressive candidate.

Image source, Joshua Lott/Getty Images

It's after midnight here in Washington DC (they're an hour behind us in Iowa) and we don't yet have a winner there - so what's going on?

• Iowa caucus voters have selected candidates in 1,678 precincts across the states
• Results are delayed: the Iowa Democratic Party says the delay is due simply to "a reporting issue"
• The BBC has been told there were serious issues state-wide with a reporting app
• Still, almost all of the Democratic candidates have taken the absence of results - and an actual winner - to make their own speeches
• We are still waiting

This new statement is out from the Trump campaign:

"Democrats are stewing in a caucus mess of their own creation with the sloppiest train wreck in history.

"It would be natural for people to doubt the fairness of the process. And these are the people who want to run our entire health care system?

"Tonight President Trump posted a record performance in the well-run GOP Iowa caucuses with record turnout for an incumbent."

Iowa Democratic Party (IDP) officials say they "found inconsistencies in the reporting of three sets of results," but we're hearing something slightly different from local district officials.

An app that was planned for results posting has "crashed" says the chairman of Dallas County, forcing officials to wait in long call queues.

Every precinct official is forced to call in or email results, and some are sending volunteers to help the IDP tabulate results.

"It doesn't really work," says the Black Hawk County chairman. "No one can reach the state party to report."

This tallies with what one official in Warren County told our correspondent Gary O'Donoghue earlier: she said she had given up trying to use the new results reporting app and was going to try and ring them in instead.

Anthony Zurcher
BBC News, Iowa

The Democratic Party establishment spent the past few days hand-wringing over what they might view as a doomsday scenario where outsider Bernie Sanders posted a solid win in the Iowa caucuses. It turns out they’re heading toward an outcome much worse than that.

Almost four years after having their party servers hacked by Russians in an attempt to disrupt the 2016 election, a “quality control issue” has derailed the reporting of Iowa caucus results.

It’s not a good look for the Democratic Party – or for American democracy.

It will be a snafu that launches a thousand conspiracy theories and leaves a race that might have received some clarity after a year of campaigning a muddled mess as the primary season gets underway.

Bernie Sanders has come on stage in Iowa to the song Power to the People.

"Let me begin by stating that I imagine, have a strong feeling, that at some point the results will be announced.

"And when those results are announced I have a good feeling we are going to be doing very very well here in Iowa.

"The message that Iowa has sent to the nation is a message shared by the American people. That we want a government that represents all of us, not just wealthy campaign contributors and the one percent."

Trump, he says "does not understand the constitution" and is "trying to divide people up based on the colour of their skin, their religion ,their sexual orientation or where they were born."

"All of that hatred, that divisiveness, is going to end when we're in the White House," he says to huge applause.

Image source, Getty Images

Introduced by her grandchildren, Senator Elizabeth Warren again took to the stage to Dolly Parton's hit song 9 to 5 in the midst of an unexpected delay in results.

"It is too close to call, so I'm just going to tell you what I do know," Warren said, her opening comment quickly met with a spirited "You won!" from a supporter in the crowd.

"As the baby daughter of a janitor I am so grateful to be up on this stage tonight," she said, pushing her message of unity in the absence of a clear Democratic winner out of Iowa.

"Tonight, as a party, we are one step closer to defeating the most corrupt president in American history," she said.

"Our union is stronger than Donald Trump."

Joe Biden just wrapped up his speech, calling for Americans to "rebuild the backbone of this country. The middle class, they've been getting laid out badly by this administration."

"We choose hope over fear," he continued. "We choose science over fiction. Unity over division. And compassion over cruelty."

"And most importantly of all: truth over lies."

Elizabeth Warren is also speaking now - candidates are filling the space created by the delay in results.

A statement from the Iowa Democratic Party says the delay in reporting caucus results is the result of a “reporting issue” and not because of a “hack or an intrusion”.

There were "inconsistencies in the reporting of three sets of results", the party said.

"Hello everyone," Joe Biden says as supporters chant "we want Joe".

"Well it looks like it might be a long night but I'm feeling good.

"I wanna make sure they're very careful in their deliberations," he says about vote counters.

"Our indication is it's going to be close. We're going to walk out here with our share of delegates."

Speaking in Iowa, where we are still awaiting results, candidate Amy Klobuchar says: "We don't win by out-dividing the divider in chief," referring to Donald Trump.

The important thing, she says, is that "the people who are sick of the name calling and the mud-slinging have the candidate they need for November.

"Our democracy cannot tolerate another four years of a president trying to bulldoze right through it."

Trump's "playbook is to divide and demoralise. Well I have a playbook too, and it says to unite and lead."

The Minnesota senator is the first candidate to find a podium amid a delay in announced results.

Nick Bryant
BBC News, Des Moines

If we don't get a clear cut result going into New Hampshire next week we're basically back at the same place we were before tonight.

Conventional wisdom had been that Iowa caucuses are some great communal act of democracy. But this delay leads to a new thinking taking over: this system sucks.

People say Iowa's residents are considered very civic minded. They give all the candidates a very close look. But the truth is that a relatively small number even turn up in the first place. So now we're back to where we often end up - debating whether the Iowa caucuses should even happen this way.