What caused the Baltimore bridge collapse?

The vessel had just departed from the berth and made a turn before hitting the bridge, a Singapore-based shipping expert, who has sailed cargo ships through Baltimore's port many times, told the BBC.

Having seen the footage, he said there were a few possible causes such as main engine failure, steering failure, generator blackout, and possibility of pilot or human error.

Speaking on the basis of anonymity, he said, "It's an unusual turn. Before a ship departs, we are supposed to carry out all the checks on all elements of the vessel before it departs. It's part of the departure checklist. So, if everything was done, something was obviously overlooked."

"These ships are so huge that even if the speed is slow, the momentum would be huge," he added.

When questioned about the last structural check of the bridge, he said, "Having a port right next to the bridge with ships going underneath it all the time – it should have been checked often."