TheCable

The Francis Scott Key Bridge in Baltimore, United States, collapsed early Tuesday morning after it was struck by a large cargo ship.

Footage obtained by CNN showed how sections of the 1.6 mile-long (about two kilometres) four-lane bridge buckled inwards, shearing away from the rest of the structure before plunging into the darkness of the water, just before dawn.

Up to 20 people and several vehicles have fallen into the river, according to the Baltimore City Fire Department, which has declared the accident a “mass casualty event”.

Kevin Cartwright, director of communications for the fire department, said its main focus right now is “trying to rescue and recover these people”.

He said it appears there are “some cargo or retainers hanging from the bridge,” creating unsafe and unstable conditions, and that emergency service workers are operating cautiously as a result.

“This is a dire emergency,” he added.

“This happened at 01:30 a.m. with limited visibility so we are working aggressively, considering the environmental temperatures as well as the water temperatures to try and rescue and perhaps recover individuals,” Cartwright said.

“It feels like at least about 30 degrees (-1°C) where I am. It could be slightly lower than that. And I’m sure that the water temperature is even colder… And that can pose a concern and risk for our divers.”

The Maryland Transport Authority said all lanes on the Interstate 695 — the road which runs across the bridge — have been closed and traffic is being rerouted.

The bridge was opened in 1977 and is named after the author of “The star-spangled banner,” the US anthem.

Francis Scott Key is believed to have sat near the site of the bridge as he witnessed the bombardment of Fort McHenry in 1814, inspiring him to write the words of the country’s anthem.