Why did the Baltimore bridge collapse and what do we know about the ship?

Baltimore's Francis Scott Key bridge collapsed early on Tuesday after a container ship smashed into the four-lane span, plunging cars into the river.

WHAT HAPPENED IN BALTIMORE?

At 1:30 a.m. ET (0530 GMT), a container ship named the Dali was sailing down the Patapsco River when it struck a pylon of the bridge, crumpling almost the entire structure into the water. There was no indication of terrorism, police said.

ARE THERE ANY CASUALTIES?

The headlights of vehicles could be seen on the bridge as it crashed into the water and the ship caught fire.

Baltimore officials said at least seven vehicles plunged into the water. As many as 20 people could be in the river. At least one person was seriously injured.

WHAT DO WE KNOW ABOUT THE SHIP THAT WAS INVOLVED?

The Dali was scheduled to sail on shipping company Maersk's route to Sri Lanka, the Danish company's website showed.

The registered owner of the Singapore-flagged ship is Grace Ocean Pte Ltd and the manager is Synergy Marine Group, LSEG data show. The ship is 948 feet (289 meters) long and was stacked high with containers.

All its crew members, including the two pilots, have been accounted for and there were no reports of any injuries.

WHAT DO WE KNOW ABOUT THE BRIDGE THAT COLLAPSED?

The Francis Scott Key bridge is a four-lane structure that sits 185 feet (56 meters) above the river. It opened in 1977 and crosses the Patapsco River, where U.S. national anthem author Francis Scott Key wrote the "Star Spangled Banner" in 1814 after witnessing the British defeat at the Battle of Baltimore and the British bombing of Fort McHenry.

The bridge carries 11.3 million vehicles a year, according to the Maryland Transportation Authority, on the I-695 highway that circles Baltimore, also known as the Baltimore Beltway.