Officials investigating the Baltimore bridge collapse have begun checking the cargo ship for hazardous materials onboard when it crashed into the structure.

The National Transportation Safety Board (NTSB) sent a team of investigators to examine the Dali vessel while it was docked in Baltimore, Maryland, on March 28.

They said the focus was on the inspection of hazardous materials aboard the vessel and the retrieval of crucial voyage data from its recorder.

The Dali reportedly lost power before ramming into a support pillar of the Francis Scott Key Bridge, plunging the structure into the river as it fell apart within seconds early morning on March 26.

The ship's pilot reportedly issued a 'mayday call' minutes before the collision, allowing Maryland transportation officers to stop oncoming traffic onto the bridge.