A search and rescue effort is underway after the Francis Scott Key Bridge on Interstate 695 in Baltimore collapsed early Tuesday when it was struck by a ship , causing a number of vehicles to plunge into the Patapsco River below.

Eight people are believed to have fallen into the water following the collapse just before 1:30 a.m. Six of those individuals remained unaccounted for as of 10 a.m. local time, authorities said at a press conference.

The eight people were part of a construction crew filling potholes, said Maryland Transportation Secretary Paul Wiedefeld. Their work had nothing to do with the structure of the bridge, which was up to code, Gov. Wes Moore said.

Two of those people were pulled from the water, said James Wallace, fire chief of Baltimore City Fire Department (BCFD), at an earlier press conference. One person was uninjured and refused treatment, while the other was transported to a local trauma center and is in very serious condition.

Footage shared on social media showed the moment of the collapse:

The ship lost power and sent out a mayday call immediately before colliding with the bridge. This alert prompted workers on the bridge to stop vehicles from continuing onto it, said Moore.

These people are heroes, he said of those workers.

Dive teams were at the scene, with sonar having detected the presence of submerged vehicles, Wallace said earlier. The temperature at the port was around 30 degrees Fahrenheit at the time of the incident.

BCFDs Wallace, speaking with CNN, said they had detected three passenger vehicles, a cement truck and a fifth vehicle submerged in the water using infrared and sonar technology. Authorities have not said whether there could be people trapped inside.

This is an unthinkable tragedy, Mayor Brandon Scott said. We have to first and foremost pray for all of those who are impacted.

Baltimore Chief Richard Worley said, Theres absolutely no indication that theres any terrorism or that the ship crash was intentional.

Moore also said that a preliminary investigation points to an accident.