A portion of Baltimore's Francis Scott Key Bridge collapsed after it was struck by a large container ship early Tuesday morning, sending several vehicles and people into the water below, authorities say.

At a press update near the bridge, officials said two people had been rescued, but others are believed to still be in the water. The number of those missing fluctuated between seven and 20.

“This is a dire emergency,” Baltimore Fire Department director of communications Kevin Cartwright told the Associated Press. “Our focus right now is trying to rescue and recover these people.” He called the collapse a “developing mass casualty event.”