Police Service of Northern Ireland (PSNI) Chief Constable Simon Byrne says he is "deeply sorry" about the breach of data on an "industrial scale" but will not resign
Byrne says police cannot verify a claim that dissident republicans have the PSNI staff list
Earlier, Byrne attended a behind-the-doors meeting with the 19-Person Policing Board which lasted almost four hours
The details of 10,000 police officers and staff were mistakenly revealed on the internet on Tuesday
A further breach was revealed on Wednesday when it emerged a police laptop and documents had been stolen from a car last month
More than 300 police officers were murdered during the Troubles and officers and staff remain under threat from republican paramilitaries
You can watch the press conference live by clicking play at the top of this page
Julian O'Neill
BBC News NI Home Affairs Correspondent
We believe the Policing Board meeting with Simon Byrne has just ended.
One member tells me Mr Byrne is not going anywhere and it seems his position was not an issue for the board today.
Sara Girvin
BBC News NI, from Policing Board meeting
We thought that we might have heard from Chief Constable Simon Byrne, who came home early from a family holiday, to be here.
But almost four hours later, he is still being questioned by politicians about these data breaches.
Breaches, that we know, have caused shock and fear among police officers.
They will be listening very, very carefully indeed to what the chief constable has to say, and they will be looking for him to restore trust.
We are expecting to hear from him after this meeting finishes but be aware, we were expecting to hear that several hours ago.
It's probably a signal of the severity of recent events in the PSNI that the Northern Ireland Policing Board meeting - which began at 10:00 - is still going on. That meeting is being held in private, so we don't know the details, but the members have been questioning PSNI Chief Constable Simon Byrne.
We do know that when it finishes Mr Byrne and the board's chair Deirdre Toner are due to face the media. For now we're playing the waiting game, but whenever we hear or see movement we'll let you know.
Today's press conference is expected to feature not only Simon Byrne but also the chair of the NI Policing Board, Deirdre Toner.
The board is holding a meeting to question Mr Byrne on the events of the past few days. That meeting is being held in private, with no media allowed in, and is running extremely long - initially we were expecting the press conference to begin after 12:00 but there's no sign of the meeting being over yet, almost three-and-a-half hours after it begun.
The Policing Board is an independent public body that oversees policing in Northern Ireland. It's made up of 10 political, and nine independent members.
It‘s main responsibilities are to:
We are hearing there is a delay in the press conference getting under way.
What was to have been a two-hour meeting is still going on - it started at 10:00.
Journalists had been advised that the press conference would start after 12:00 but it's going to be well after 13:00 by the looks of it.
Image source, PAOne question asked at today's Policing Board meeting will be about Simon Byrne's position as chief constable.
Former police detective Alan Maines tells BBC Radio Ulster's Talkback programme that it isn't the right time for change, and Byrne should "stand up and use the resilience he seems to have" to guide his officers and the community through this period.
Belfast Telegraph crime correspondent Allison Morris says the opinion of officers is key to Byrne keeping the job.
Officers are already struggling with low morale, a high level of sickness, and safety concerns among other issues, she argues.
Former Northern Ireland justice minister David Ford does not think now is time to speculate on Byrne's position and the priority should be ensuring there is a robust examination of why the leak happened.
Julian O'Neill
BBC News NI Home Affairs Correspondent
The PSNI chief constable was questioned by journalists on the way into this morning's Policing Board meeting.
Asked by one reporter if he would resign, he replied: "I'll deal with that later."
But the damage caused by these breaches could run into tens of millions of pounds.
Simon Byrne has been here before, regarding questions of his leadership.
He has said before that he is not for quitting; he is seeing this job through.
Image source, Liam McBurney/PA MediaChief Constable Simon Byrne arriving earlier for the meeting
The press conference, which follows the emergency meeting of the Northern Ireland Policing Board in Belfast, was expected to happen shortly, but we understand the meeting is still going on. We'll let you know when we hear more.
When it does begin, just click the play button at the top of this page.
As always, we will be bringing you the key points from the meeting and press conference as we get them.
Image source, CHARLES MCQUILLANPolice Service Northern Ireland worried about data breach
These data breaches are a serious development for PSNI officers who already follow a strict regime when it comes to security.
But where does this risk come from? For the most part, it is from dissident republican groups who consider officers "legitimate targets".
After one dissident group, the New IRA, claimed responsibility for the most recent shooting of Det Ch Insp John Caldwell in Omagh in February, the terrorism threat level in Northern Ireland was raised from substantial to severe, meaning an attack is highly likely.
More than 300 police officers were targeted and killed in Northern Ireland during the period of conflict known as the Troubles.
The police feel they still operate in a threatening environment.
Deputy Chief Constable Mark Hamilton said dissident republicans were focused on attacking police officers, not the public.
With this in mind, now that there is the possibility of officer’s identities being in the hands of these groups, PSNI rank and file are left feeling vulnerable and worried for the safety of themselves and their families.
Image source, PA MediaAll eyes will be on the PSNI chief constable today as he speaks for the first time since this crisis began on Tuesday.
It won’t be the first major controversy Simon Byrne has faced during his time in the top job.
Byrne, who has held top ranks in English police forces over 36 years, started in the role in early 2019. His tenure has been marked by a number of high profile incidents:
Despite these issues, the chief constable has stayed the course and was even linked with one of the biggest jobs in UK policing, head of the Metropolitan Police.
In May, his contract as chief constable was extended to 2027. If he stays for that long, he will become the PSNI's longest-serving chief constable.
Image source, Getty ImagesNorthern Ireland’s Assembly may not be sitting but there’s been huge political reaction to this leak – with most politicians asking the same thing – how could this have happened?
Ulster Unionist Party MLA and Policing Board member Mike Nesbitt says work is ongoing to try to figure out the electronic fingerprints that will lead the the PSNI to figure out who accessed the data – but he adds “what you do thereafter is an open question we will try to explore with them”.
Sinn Féin assembly member Gerry Kelly says he will be asking why “safeguards were not in place to prevent such a breach happening and how quickly measures can be put in place to ensure it won't happen again".
Trevor Clarke from the Democratic Unionist Party says while any breach is “unacceptable” it is more so when “it discloses personal information identifying rank-and-file officers".
The Alliance Party leader and former Justice Minister Naomi Long, says that the most urgent issue is “supporting those whose security has been compromised".
Social Democratic and Labour Party leader Colum Eastwood tweeted: "The level of incompetence involved here is staggering. So dangerous.”
Many police officers are worried about this leak.
The Police Federation for Northern Ireland is the body that represents PSNI officers - its chair Liam Kelly said there are widespread concerns about personal security.
“I understand several hundred officers now have approached their management to record those concerns,” he told Radio Ulster.
“Going forward if it results in officers having to move location, or worst-case even moving house out of this, at that point I would be made aware of that,” he said.
However he added that these are the early stages of this incident so it’s too early to tell what the outcome will be.
Image source, PA MediaAny data breach of personal details is a serious matter but these PSNI breaches have an extra level of concern - they involve the identities of police officers and PSNI staff, and could put them in danger.
Officers have been targeted in the past by dissident republicans, with the latest attack taking place in February when Det Ch Insp John Caldwell was shot several times - he survived but with life-changing injuries.
So how has this story developed?
Read more: How did the police data breach happen?
Image source, PA MediaIt's been a challenging couple of days for the Police Service of Northern Ireland (PSNI).
It has emerged that two major data breaches have led to the identities of several thousand police officers potentially entering the public domain.
With many officers keeping their occupation secret, due to a possible threat from dissident republicans, the breaches could represent a major risk to their safety.
PSNI Chief Constable Simon Byrne will face media questions for the first time since the crisis broke - we’re expecting him to be speaking at some point after 12:00.
Stay with us for all the latest.