Emergency services combed the cold waters of Baltimore harbour on Wednesday in search of the bodies of six men – all reported to be Latin American immigrants – presumed killed when a giant cargo ship slammed into the bridge where they working the night shift fixing potholes.

Police and Coast Guard crews swarmed the disaster site, with specialised divers scouring the river under the destroyed Francis Scott Key Bridge. Their task, however, was limited to recovering bodies.

"We do not believe any of these individuals are still alive," the regional Coast Guard chief, Rear Admiral Shannon Gilreath, said.

The container ship Dali, almost a kilometre long and piled high with cargo, was leaving the busy port at 1:30 am on Tuesday en route to Asia when power failed and the vessel crashed straight into one of the columns supporting the steel bridge – a major crossing point used by tens of thousands of motorists a day.

Nearly the entire structure collapsed instantly, cascading over the bow of the ship, which remained entangled in the debris on Wednesday, blocking one of the busiest US trading ports.

In dramatic scenes, police managed to stop vehicles from driving onto the bridge as soon as they received a Mayday call from the ship to warn of the impending collision.

But there was no chance to evacuate the eight men filling potholes on the road directly above the massive ship.

Officials said that two of them were pulled from the water, one of them seriously injured and the second unharmed. The other six vanished into the swirling currents and crumpled tangle of wrecked girders and pylons. (AFP)