Recovery efforts have resumed over six construction workers who are presumed dead after a cargo ship hit a pillar of the Francis Scott Key Bridge in Baltimore, Maryland, causing the structure to collapse.

The collision occurred in the early hours of Tuesday after the ship lost its steering capability before it hit a pillar of the US city’s Francis Scott Key Bridge.

Audio from first responders reveals a scramble to halt traffic just before the crash.

The bridge is an important link in the region’s transportation infrastructure, and its collapse is expected to snarl commuter traffic and disrupt a vital shipping port for some time.

Maryland Bridge Collapse
Six people are feared dead (AP)

Within 90 seconds of a dispatcher’s 12-second warning over the radio on Tuesday, police officers responded that they had managed to stop vehicle traffic over the Baltimore bridge in both directions. One said he was about to drive onto the bridge to alert a construction crew.

But it was too late. Powerless and laden with huge containers, the vessel smashed into a support pillar.

“The whole bridge just fell down,” a frantic officer said. “Start, start whoever, everybody … the whole bridge just collapsed.”

When the container ship Dali slammed into the pillar at around 1.30am on Tuesday (5.30am GMT), it caused a long span of the bridge, a major link in the region’s transport networks, to crumple into the Patapsco River.

At least eight people went into the water. Two were rescued but the other six, part of a construction crew that had been filling potholes on the bridge, are missing and presumed dead.

A search for their bodies was under way on Wednesday morning, according to Maryland State Police spokesperson Elena Russo.

Among the missing were people from Guatemala, Honduras and Mexico, according to diplomats from those countries. The Honduran man was identified as Maynor Yassir Suazo Sandova.

Federal and state officials said the crash appeared to be an accident. The National Transportation Safety Board is investigating, and ship traffic entering and leaving the Port of Baltimore has been suspended indefinitely.

Capt Michael Burns Jr of the Maritime Centre for Responsible Energy said bringing a ship into or out of ports in restricted waters with limited room to manoeuvre is “one of the most technically challenging and demanding things that we do”.

A US flag flies before the wreckage
Two people were rescued from the water (AP)

“So there really is few things that are scarier than a loss of power in restricted waters,” he said.

And when a ship loses propulsion and steering, “then it’s really at the mercy of the wind and the current”.

Video showed the ship moving at what Maryland governor Wes Moore said was about 9mph toward the 1.6-mile bridge. Traffic was still moving across the span, and some vehicles appeared to escape disaster with only seconds to spare.

The crash caused the span to break and fall into the water within seconds, and jagged remnants were left jutting up from the water.

Police said there is no evidence anyone went into the water other than the workers, though they had not discounted the possibility.

A senior executive at the company that employed the crew, Brawner Builders, said they were working in the middle of the bridge when it fell.

“This was so completely unforeseen,” said Jeffrey Pritzker, the company’s executive vice president. “We don’t know what else to say. We take such great pride in safety, and we have cones and signs and lights and barriers and flaggers.”

The crash happened long before the busy morning commute on the bridge, which was used by 12 million vehicles last year.

US Transportation Secretary Pete Buttigieg said it was too soon to give a time frame for clearing the channel, which is about 50 feet deep, while President Joe Biden said he planned to travel to Baltimore soon and expects the federal government to pay the entire cost of rebuilding.

Synergy Marine Group, which manages the ship, said the impact happened while it was under the control of one or more pilots, who are local specialists who help guide vessels safely in and out of ports.

Maryland Bridge Collapse
Inquiries are under way into the tragedy (AP)

The firm said one crew member was treated at a hospital for a minor injury.

The ship is owned by Grace Ocean Private Ltd, and Danish shipping giant Maersk said it had chartered the vessel.

The 985ft Dali was headed from Baltimore to Colombo, Sri Lanka, and flying under a Singapore flag, according to data from Marine Traffic.

Baltimore Mayor Brandon Scott called it “an unthinkable tragedy”. Governor Mr Moore said that “all of our hearts are broken for the victims and their families”, and he also hailed first responders for their quick response.

“Literally by being able to stop cars from coming over the bridge, these people are heroes,” Mr Moore said. “They saved lives last night.”