Lost power, a mayday call and the crash that brought down a Baltimore bridge

By the time the crew of the Dali, a massive 948ft (289m) container ship, realised what was happening, it was already far too late.

The vessel - at the very start of a 27-day journey from the port of Baltimore to Sri Lanka - completely lost power after leaving the port and was hurtling towards the city's iconic Francis Scott Key Bridge.

It was the middle of the night and the crew onboard were pitched into further darkness when the ship's lights suddenly went out.

The vessel was dead: there were no electronics and - crucially - no engine power. They were adrift but powerless to stop what was happening.

Multiple alarms rang out as the crew ran unsuccessful tests in a desperate attempt to fix the issue and regain power.

A local pilot onboard the vessel frantically gave orders, telling the crew to steer the rudder hard to port and drop anchor to keep it from drifting starboard.

While an emergency generator is believed to have kicked in, the ship never regained the use of its engines.

The pilots were left with no choice. Shortly before 01:30 (05:30 GMT), they issued a mayday call warning authorities that a collision was imminent.

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"There's a ship approaching that has lost their steering," an official with the Maryland Transportation Authority can be heard saying in radio traffic recorded not long after. "Until you've got that under control, we've got to stop all traffic."

Maryland Governor Wes Moore later hailed the crew as "heroes" and said that their quick response had "saved lives" because authorities were able to stop the flow of vehicle traffic on to the bridge in the two minutes between the call and the collision.

It did not, however, stop what happened when the Dali slammed into a concrete column on the 1.5-mile (2.4km) bridge, which quickly collapsed, piece by piece, into the dark, cold waters of the state's Patapsco River.

Six people - all believed to be members of a road crew working on the bridge - are presumed dead due to the water temperature and time that has passed. The US Coast Guard said in the late evening on Tuesday that it had concluded the men had died and intended to suspend its massive search and rescue effort, which had been complicated by cold and cloudy weather.

Local media had reported that the six workers were citizens of Mexico, Guatemala, Honduras and El Salvador. The BBC has not independently confirmed this and has contacted consular authorities for comment. All 22 crew on the ship were Indian - the country is a major player in the global seafaring industry.

The ship's crew were all accounted for and none appeared to suffer significant harm.

The dramatic destruction of the bridge - which opened 47 years ago - left many in the city, including Governor Moore, shaken.

"This is a place that is a normal commute route for 30,000 Marylanders every single day. To hear the words 'the Key Bridge has collapsed' is shocking. It's heartbreaking," Mr Moore said at a news conference on Tuesday.

"For over 47 years, it is all that we've known."

Maryland Governor Wes Moore and Baltimore Mayor Brandon Scott were at the scene on Tuesday

What exactly led to the loss of power on board the Dali remains unclear.

Jennifer Homendy, the chair of the National Transportation Safety Board, said that investigators would now seek to examine data from a voyage data recorder.

"It's a critical piece of our investigation," she said, adding that for now, the inquiry remains "about people".

"It's about families and addressing the needs of those that were impacted."

As the sun rose over Baltimore on Tuesday morning, residents of the diverse and strongly working-class areas near the bridge expressed shock at the scene they had woken up to.

"I felt it… The whole house shook," John Flansburg, who lives near the water, told the BBC. "Today's not going to be a good day. A lot of tragedy."

Another area resident, Darlene Irwin, said that she first knew there was a problem when she heard a "rumbling sound".

Hours later, the scale of the destruction became apparent when she looked out her window at the Patapsco River. The massive cargo ship, carrying at least 3,000 containers, was wedged between the debris of the collapsed bridge.

By then, the entire area had become the scene of a massive search and rescue effort, with police boats criss-crossing the river and police and Coast Guard helicopters flying overhead.

At least six people are still missing. They are believed to be members of a road crew working on the bridge at the time of the collapse

At a local school, two US military UH-60 Blackhawk helicopters were parked in a sports field, their camouflage-clad pilots and crew milling next to the aircraft.

"To see it now in the daylight," Ms Irwin said, "it is just tragic."

While officials have repeatedly stressed that their focus remains on the search for the missing, experts have warned that the incident could also have a significant impact on the port of Baltimore, one of the busiest on the US east coast.

Maryland Senator Ben Cardin told reporters that the re-opening of the waterway would be "critical" for the US economy.

The port is a key regional hub for goods ranging from steel and aluminium to agricultural equipment, and is used by car-makers including General Motors and Honda. Data from the Maryland Port Administration shows the port handled at least 750,000 vehicles last year.

"This will disrupt vessel schedules and strain handling capacities at other ports such as Philadelphia and Norfolk," said Mirko Woitzik, global director of intelligence for Everstream Analytics, which provides supply-chain services.

"[This could] lead to spillover congestion and delays that could last months."

Speaking at the White House on Tuesday, US President Joe Biden - who said he had commuted over the bridge "many, many times" between his home state of Delaware and Washington - vowed to "move heaven and earth" to re-open the bridge.

"We're going to spend all the federal resources they need as we respond to this emergency," he said. "And we're going to rebuild that port together."

Mr Biden added that 15,000 US jobs "depend on that port".

Officials have so far declined to comment on any potential timeline for that to happen.

Authorities say that, for now, they are fully focused on the search and rescue operation.

Mr Moore, for his part, said only that the recovery process "will not be short". Baltimore, he acknowledged, was facing a "long road" after the collapse.

This is not the first time the Dali has been involved in an incident.

According to Vessel Finder, a tracking website, the ship was involved in another collision in the Belgian port of Antwerp in 2016. There were no injuries or significant damage reported at the time.

As night fell on Tuesday, the ship and its load of 3,000 containers remained on the Patapsco River, its nose stuck between the mangled debris of the bridge it brought down in seconds.