Baltimore, Maryland - A major bridge in Baltimore collapsed Tuesday after a ship collided with it, crashing into water below and seemingly bringing vehicles with it.

Dramatic CCTV footage shows what appears to be a container ship hitting a footing of the Francis Scott Key bridge, sending it plunging into the Palapsco river, followed by the greater part of the massive structure.

Lights from what appear to be vehicles can be seen on the road surface as the bridge warps and crashes in sections, with the third tranche cantilevering upwards before it, too, tumbles into the water.

"We have reason to believe that there were vehicles and possibly a tractor-trailer that went into the water," Kevin Cartwright of Baltimore Fire Department told the Baltimore Sun, adding "the entire bridge" had collapsed.

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"I can confirm at 1:35 am, Baltimore City police were notified of a partial bridge collapse, with workers possibly in the water, at the Francis Scott Key Bridge," Detective Niki Fennoy said.

A Baltimore Fire Department spokesperson said up to 20 people were in the water, while fire chief James Wallace said they were "looking for upwards of seven individuals.

The 1.6-mile, four-lane bridge spans the Patapsco River southwest of municipal Baltimore. It opened in 1977 and carries more than 11 million vehicles a year.

The Maryland Transportation Authority told drivers to avoid the bridge, part of the I-695 interstate highway, which it called an "active scene".

Ship monitoring website MarineTraffic showed a Singapore-flagged container ship called the Dali stopped under the bridge early Tuesday.

Baltimore Mayor Brandon Scoot and Baltimore County Executive Johnny Olszewski Jr. both said they were aware of the incident and that rescue efforts were underway.

"Please pray for those impacted," Olszewski posted on X.

As daylight broke over the search and rescue operation with divers in the water looking for survivors, the horrifying extent of the incident became apparent.

Twisted stanchions of steel lay draped over the deck of the ship, on which stacks of containers teetered precariously – adding an extra dimension of danger to rescue and recovery work.

Baltimore Mayor Brandon Scott said the incident was an "unthinkable tragedy," adding "we have to be thinking about the families and people impacted, folks who we have to try to find."

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He described images of the collision as "like something out of an action movie."

The footage appeared to show the ship going dark twice in the moments before the collision, possibly indicating some kind of power failure on board.

There was no immediate confirmation of the cause of the disaster, but Baltimore's Police Commissioner Richard Worley said there was "no indication" of terrorism.

Maryland Governor Wes Moore declared a state of emergency, a move that will ease the release of federal resources.