Divers recover two bodies after US bridge collapse

Divers have recovered the remains of two of the six workers missing since they were tossed from a highway bridge that collapsed when a faltering cargo freighter rammed into the structure.

The bodies were pulled from the mouth of the Patapsco River on Wednesday, a day after the massive container ship lost power and its ability to manoeuvre before ploughing into a support pylon of the Francis Scott Key Bridge, knocking most it into the water below.

Maryland State Police Colonel Roland Butler said a truck containing the bodies of the two men was found in about eight metres of water near the midsection of the fallen bridge.

He said authorities suspended search efforts because of increasingly treacherous conditions in the wreckage-strewn river.

Sonar images showed additional submerged vehicles "encased" in fallen bridge debris and superstructure, making them difficult to reach, Butler said.

The two men recovered were Alejandro Hernandez Fuentes, 35, of Baltimore, a native of Mexico, and Dorlian Ronial Castillo Cabrera, 26, of nearby Dundalk, originally from Guatemala.

Four more workers who were part of a crew filling potholes remain missing and are presumed dead.

The Dali is stuck under part of Francis Scott Key Bridge
A bridge work crew was repairing potholes when the ship ploughed into the bridge. (AP PHOTO)

The six workers also included immigrants from Honduras and El Salvador, officials said.

Rescuers pulled two workers from the water alive on Tuesday, and one was hospitalised.

The collapse forced an indefinite closure of the Port of Baltimore, one of the busiest on the US eastern seaboard, handling more automobile and farm equipment freight than any other in the country.

Earlier on Wednesday, federal investigators boarded the freighter - still anchored in the harbour channel with part of the mangled bridge splayed over its bow - to begin interviewing the ship's 22 crew members, who remained aboard the vessel.

National Transportation Safety Board personnel recovered the vessel's "black box" data recorder, which they hope will help form a precise timeline of the accident.

Details emerged of the intense efforts to save lives in the minutes before the steel bridge collapsed, from recordings of radio chatter by authorities after they were alerted that the cargo ship Dali was drifting out of control towards Key Bridge.

"Hold all traffic on the Key Bridge. There's a ship approaching that just lost their steering," someone is heard saying over a police radio minutes before the 1.30am crash on Tuesday.

Police boats near a cargo ship under the Francis Scott Key Bridge
Authorities suspended the search because of worsening conditions in the wreckage-strewn river. (AP PHOTO)

While voices were heard discussing next steps, including alerting any work crews to leave the bridge, one broke through to say: "The whole bridge just fell down!"

The recording offered a glimpse of how authorities scrambled before the crash sent the six bridge-repair workers to their deaths in the frigid waters.

The Singapore-flagged Dali reported a loss of power before impact and dropped anchor to slow the vessel, giving authorities barely enough time to halt road traffic on the bridge and likely preventing greater loss of life.

As well as halting port operations, the collapse created a traffic quagmire for Baltimore and the densely populated region.

NTSB chair Jennifer Homendy said her team had also begun interviewing survivors and emergency responders.

The US Coast Guard priorities were to restore the waterway for shipping, stabilise the vessel and extricate it, Vice Admiral Peter Gautier said at a White House briefing.

The ruins of the bridge needed to be cleared from the vessel before it could be moved, he said.

A truck enters the Sea Girt Marine Terminal Port of Baltimore
The disaster closed the Port of Baltimore, one of the busiest on the US eastern seaboard. (EPA PHOTO)

The wreck raised questions about the ship's previous operations, but Gautier said it had a "fairly good safety record".

Of the ship's 4700 cargo containers, 56 held hazardous materials but there was no threat to the public, he said.

Two containers went overboard but they did not contain hazardous materials.

The ship was carrying more than 5.7 million litres of fuel oil, Gautier said.

Homendy said the NTSB would also examine whether contaminated fuel played a role in the ship's power loss.

The Port of Baltimore handles more automobile freight than any other US port - more than 750,000 vehicles in 2022, as well as container and bulk cargo ranging from sugar to coal.

Still, economists and logistics experts doubt the port closure will unleash a supply chain crisis or spike in the price of goods due to ample capacity at rival shipping hubs along the eastern seaboard.