The landmark Francis Scott Key Bridge in the US city of Baltimore has collapsed after a cargo ship collided with it.
Several vehicles that were crossing the bridge, which is more than 2.6km (1.6 miles) long, plunged into the waters of the Patapsco River.
As many as 20 people are believed to be in the water, according to Baltimore fire department.
Emergency personnel rushed to the scene and rescue operations are under way.
City officials say that at around 01:30 local time (05:30 GMT) a ship struck a column on the 47-year-old bridge, causing it to collapse.
A number of vehicles, including “one the size of a tractor-trailer” plunged into the water below, they added.
The container ship, named by ship tracking data as the Singapore-flagged Dali, was on its way to Colombo in Sri Lanka.
On marine radars, it departed from the terminal at Port Breeze at around 00:45.
The massive rescue operation is being led by Baltimore fire department, the US Coastguard and other agencies from the state of Maryland.
The head of communications for Baltimore fire department, Kevin Cartwright, described the situation as a “dire emergency”.
“Our focus right now is trying to rescue and recover these people,” he said, referring to those believed to be in the water.
Mr Cartwright said there were “some cargo or retainers hanging from the bridge”, creating unsafe and unstable conditions, and that emergency rescue teams were operating cautiously as a result, amid a power cut.
Shipping company Synergy Marine Group said all crew members, including the two pilots who were aboard, had been accounted for and there were no reports of any injuries, adding that “the exact cause of the incident is yet to be determined”.
