At least seven people were missing after a major bridge in the U.S. city of Baltimore collapsed after it was hit by a container ship early Tuesday.

The vessel appears to have hit one of the supports of the Francis Scott Key Bridge, causing the roadway to break apart in several places and plunge into the water, according to a video posted on X, formerly known as Twitter. The ship caught fire and appeared to sink.

The bridge, which opened in 1977, spans the Patapsco River, a vital artery that along with the Port of Baltimore is a hub for shipping on the East Coast. It is named for the writer of "The Star-Spangled Banner."

"This is a dire emergency," Kevin Cartwright, director of communications for the Baltimore Fire Department, told The Associated Press. "Our focus right now is trying to rescue and recover these people."

He added that some cargo appeared to be dangling from the bridge.

Emergency responders were searching for at least seven people believed to be in the water, Cartwright said, though he added it was too early to know how many people were affected. He called the collapse a "developing mass casualty event."

He said agencies received 911 calls around 1:30 a.m. reporting that a ship leaving Baltimore had struck a column on the bridge. Several vehicles were on the bridge at the time, including one the size of a tractor-trailer truck.

Mayor Brandon M. Scott and Baltimore County Executive Johnny Olszewski Jr. posted that emergency personnel were responding and rescue efforts were underway.

"All lanes closed both directions for incident on I-695 Key Bridge. Traffic is being detoured," the Maryland Transportation Authority posted on X.