A CARGO ship rammed into a major bridge in Baltimore in the United States early today, causing it to collapse and plunging several vehicles into the river below.

It was not clear how many people might be in the waters of the busy harbour but rescuers pulled two people from the water by mid-morning and searched for more.

But fire chief James Wallace said authorities “may be looking for upwards of seven people” but said that number could change. 

One official called it a “developing mass casualty event.”

A social media video showed the shocking spectacle of the bridge collapsing as the ship struck. The vessel caught fire, and thick black smoke billowed out of it.

“Never would you think that you would see the Key Bridge tumble down like that. It looked like something out of an action movie,” Baltimore Mayor Brandon Scott said, calling it “an unthinkable tragedy.”

The bridge came down in the middle of night when traffic would be lighter than during the day when thousands of cars are normally crossing. 

It said that all the cargo vessel crew members, including the two pilots on board, were accounted for, and there were no reports of any injuries.