Rescuers have recovered two people from chilly waters around the collapsed Francis Scott Key Bridge in Baltimore, but six remain missing.
One person was able to walk away from the incident, but the other remained seriously injured in hospital.
The bridge was destroyed when a support pillar was hit by the 9,962-teu container ship Dali (built 2015), managed by Synergy Marine and chartered by Maersk.
Maryland transportation secretary Paul Wiedefeld said there were eight people on the bridge at the time.
Maryland governor Wes Moore said the ship was moving towards the bridge at a “very rapid speed”.
He added that crews sent an emergency signal.
Moore said this ensured more cars were stopped from crossing the bridge, averting greater disaster.
“These people are heroes,” he said. “They saved lives last night.”
At a press conference on Tuesday morning, Baltimore fire chief James Wallace said: “One individual refused service and refused transport — essentially that person was not injured.
Six more people are still unaccounted for.
Wallace said 911 call centre operators received numerous calls indicating that several people were in the waters of the Patapsco River.
At 01:50 local time, the first unit arrived on the scene and reported a complete collapse of the bridge. It became clear that people had been on the bridge at the time.
Officials earlier said there could be as many as 20 people in the water.
Police have been told that some workers were still on the bridge, but they are yet to confirm this.
“We are still very much in an active search-and-rescue posture at this point and we will continue to be for some time,” Wallace said.
“We have a large area that we have to search. This includes on the surface of the water, subsurface.”
Sonar has detected vehicles under the water, the fire chief told reporters.
It was unclear if there was a problem with the ship.
Police have not spoken to either of the two pilots on board yet.
“There is absolutely no indication this is terrorism,” Wallace said.
The FBI is involved in the investigation.
A sudden change of course sent the Dali straight into a support pillar.
Synergy said the vessel has an all-Indian crew of 22. One crew member suffered a scratch to his head.
Two members of Synergy’s US team are heading to Baltimore from Miami and Oklahoma to investigate the incident.
