Rescuers are racing to find any survivors after a major bridge collapsed in the US city of Baltimore after being struck by a heavily laden container ship.
Many questions remain, including how the ship could have strayed into the bridge. Here's what we know so far:
At approximately 1:30 am (0530 GMT) the Singapore-flagged container ship Dali, departing Baltimore en route to Sri Lanka, crashed into a concrete pier supporting the Francis Scott Key Bridge in Baltimore.
Within seconds almost the entire bridge collapsed, sending multiple vehicles and people plunging into what officials said was roughly 50 feet (15 meters) of frigid water below.
A search and rescue operation involving divers, boats, aircraft and sophisticated sonar and infrared equipment is under way.
It's unclear, but officials say they are searching for at least seven people.
Two people have already been pulled from the water. One was unhurt, but the other was seriously injured and has been rushed to hospital.
The lights from multiple vehicles can be seen on the bridge in the CCTV footage seconds before the collapse. Some contractors were working on the bridge at the time, Maryland officials said.
Baltimore's fire chief James Wallace said sonar has found vehicles submerged in the water, but he could not say how many.
The managers of the Dali, Synergy Marine Group, said that none of the crew were injured.
We don't yet know -- though officials have said repeatedly that there is "no indication" of terrorism.
CCTV footage shows the ship going dark twice in the minutes before, possibly indicating some kind of power failure on board.
Synergy Marine Group said the cause "has yet to be determined."
Some experts suggested the bridge's main support structures may not have been properly protected to withstand a collision by such a large vessel.
"The significant momentum of this massive cargo vessel, especially when laden with cargo, would have been considerable upon impact," said Professor Toby Mottram, a structural engineer at the University of Warwick.
"It's evident that the pier couldn't withstand the impact energy.... The extent of the damage to the bridge superstructure appears disproportionate to the cause, a matter for future investigation," Mottram said.
Authorities have closed the port "until further notice" and traffic is being diverted away from the bridge as the rescue effort continues.
Officials have said that finding any survivors is their only priority at the moment. Maryland state Governor Wes Moore declared a state of emergency.
They are also monitoring for the possibility of any fuel spill from the stricken Dali, though none has been confirmed yet.
