US authorities have released details from the black box of a ship at the centre of the Baltimore bridge disaster showing how the crew and a pilot battled to avert tragedy in a little over four minutes.

The National Transportation Safety Board (NTSB) had earlier retrieved the Maersk-chartered container ship Dali’s voyage data recorder (VDR) after the crash that collapsed the Francis Scott Key Bridge, killing six people.

Sky News reported the VDR shows the ship left the Seagirt Marine Terminal in Baltimore at 0039 local time on Tuesday (4:39 GMT).

By 0107 the vessel had entered the Fort McHenry Channel.

The Dali was then recorded on a true heading at 8 knots at 0124.

But a minute later, numerous audible alarms were recorded on the ship’s bridge audio.

At about this time, the VDR stopped recording sensor data but still picked up sound using its redundant power source.

Recording resumed a minute after this, and steering commands and rudder orders were heard.

At 0126 and 39 seconds, a pilot on board made a general VHF radio call for tug help, and the pilot association dispatcher phoned the Maryland Transportation Authority (MDTA) duty officer regarding the power loss.

By 0127, the pilot had ordered the Dali to drop the port anchor and ordered additional steering commands.

Another call was made by the pilot on VHF 25 seconds later, reporting that the ship had lost all power and was approaching the bridge.

Traffic halted

MDTA data shows that their duty officer radioed two MDTA units on each side of the bridge to halt traffic, saving an unknown number of lives.

At 0129, the Dali was travelling at just under 7 knots.

And at 0129 and 33 seconds, the VDR recorded sounds consistent with the collision with a bridge pillar.

MDTA dash cameras show the bridge lights extinguishing at that point.

At 0129 and 39 seconds, the pilot reported the bridge down over the VFH radio to the US Coast Guard.

The governor of Maryland, Wes Moore, said on Thursday night that the city has “a very long road ahead” following the tragedy.

He added: “I’m calling on everyone to do their part — in this game, no one gets to sit on the sidelines. We need every single Baltimorer and every single Marylander to help us.”

The 21 crew on board the 9,962-teu Dali (built 2015) are said to be in good health, according to India’s foreign ministry.

A total of 20 are Indian nationals, while there is also a Sri Lankan on the vessel.

Dive operations and vehicle recovery were paused on Thursday due to hazardous conditions caused by the submerged wreckage and debris.

Authorities have established a 2,000-yard safety zone around the boxship.

A “sheen” has been observed around the vessel.

NTSB said there are 56 total containers on the ship that contained hazardous materials.

Of these, 14 were impacted by the collision.