A container ship crashed into a major bridge in Baltimore, Maryland, in the early hours of Tuesday, causing large parts of it to crumble into the river below and sending several people into frigid waters.
Rescuers were searching for at least six people, but all six are now presumed dead.
Two people were rescued from the water, with one in a serious condition, officials said.
What is the Francis Scott Key Bridge?
The Francis Scott Key Bridge is a large steel structure that extends over the Patapsco River, south-east of the Baltimore metropolitan area, also known as the Baltimore Beltway.
The four-lane bridge extends across about 2.6km. Locally, it is referred to as the Key Bridge and is part of the Interstate 695 motorway. It is about an hour's drive to the north of the nation's capital, Washington.
Built in 1977, the bridge was named after the author of The Star-Spangled Banner, the American national anthem, and cost an estimated $110 million.
On its completion, it was one of the longest continuous truss bridges in the world, the National Steel Bridge Alliance said.
Why did the bridge collapse?
A Singapore-flagged container ship known as Dali crashed into one of the Key Bridge pillars at 1.30am local time on Tuesday, causing large sections of the structure to collapse.
The ship's management company Synergy Marine Group said all crew members on board had been accounted for and no injuries have been reported.
The company said that the cause of the crash has not yet been determined.
Maryland Governor Wes Moore said that crew members on the ship reported losing power when it made its mayday distress call before crashing into the bridge.
Why is the Francis Scott Key Bridge important?
Baltimore hosts one of the nation's busiest ports for total cargo, as well as value, the city says.
It is also the busiest US port for vehicle shipments. US car makers General Motors and Ford said it was going to reroute affected shipments because of the crash, Reuters reported.
In 2023, the port handled a record 52.3 million tonnes of foreign cargo valued at $80 billion, the governor's office said last month.
Crews moved 1.1 million 20-foot containers along with 847,158 vehicles and light lorries, a Maryland government website said, leading all other US ports for the 13th consecutive year.
There were 35 major bridge collapses worldwide between 1960 and 2015, 18 of them in the US, said a report from the World Association for Waterborne Transport Infrastructure published in 2018.
More than a third of US bridges need repair and about 43,000 are in poor condition and classified as “structurally deficient”, the American Road and Transportation Builders Association said.
The Federal Highway Administration rated the bridge as satisfactory and in fair condition in its most recent federal review last June, AP reported.
