The National Transportation Safety Board on Tuesday took over the investigation into the collapse of Baltimore's Francis Scott Key Bridge after a cargo ship crashed into it.

NTSB Chairwoman Jennifer Homendy updated the investigation at an afternoon news conference. She said a team of 24 investigators started arriving at the accident scene as early as 6 a.m.

The Coast Guard would help in the probe into what happened, while also continuing a search and rescue operation for the six people who remained unaccounted for after the collapse.

Homendy said the safety record of the ship and its owners will be investigated.

Investigators will also recover and analyze the ship's voyage data recorder, Homendy said. The systems are required to be installed on all modern vessels to preserve details about the ship and provide information to investigators after an accident.

"It's a critical piece of our investigation," Homendy said of the data recorder.

The Singaporean-flagged cargo vessel Dali crashed into the bridge at around 1:30 a.m. after losing power. The incident caused multiple vehicles to fall into the river below.

"We have an unspeakable tragedy," Baltimore Mayor Brandon Scott said.

Baltimore Fire Chief James Wallace said about 50 divers were in the water on Tuesday morning for the search.

By Tuesday afternoon, they had located three passenger vehicles in the water and a cement truck. There is one other possible vehicle that was located, Wallace said. It is believed that all of the vehicles were connected to the contruction crew.

The Dali lost power and declared a mayday before hitting the bridge. State officials say bridge workers immediately closed the span to vehicle traffic, likely saving lives.

Maryland Gov. Wes Moore said there was no indication of a connection to terrorism, and appeared the impact to be an accident.

Maryland Transportation Secretary Paul J. Wiedefeld said crews faced a "very tough situation" conducting rescue operations in the frigid water.

"All [Dali] crew members, including the two pilots, have been accounted for, and there are no reports of any injuries. There has also been no pollution," the firm said in a statement obtained by the shipping news outlet TradeWinds.

According to Shipwreck Log and VesselFinder, the ship was previously involved in an incident in Antwerp, Belgium, in 2016 and the ship had just left Baltimore to head toward Sri Lanka when she struck the bridge.

Baltimore Bridge Collapse 2024

Multiple vehicles fell into the water as the bridge collapsed. Authorities continued efforts Tuesday afternoon to rescue six construction workers who were doing maintenance work on the bridge at the time of the incident.

Baltimore Fire Chief James Wallace said two people were pulled from the water. One of them was able to walk away without medical care. The other person was in very serious condition at a hospital.

"There's many more we have to find," Mayor Scott said. "This is an all hands on deck situation."

"This is a dire emergency. Our focus right now is trying to rescue and recover these people," Baltimore Fire Department communication director Kevin Cartwright said, adding that it was too early to know how many people were affected but called the collapse a "developing mass casualty event."

Francis Scott Key Bridge Collapse

The Francis Scott Key Bridge was opened in 1977 and spans the Patapsco River. It is a vital artery that, along with the Port of Baltimore, is a hub for shipping on the US East Coast. The bridge carries Interstate 695 over the Patapsco.

From a vantage point near the entrance to the bridge, jagged remnants of its steel frame protrude from the water. An on-ramp now ends abruptly where the fallen span once began.

President Biden called the collapse of Baltimore's Francis Scott Key Bridge a "terrible accident" and called on Congress to support a quick rebuild with federal funds.