The National Transportation Safety Board (NTSB) said in a preliminary report that about 10 hours before leaving Baltimore the Dali experienced a blackout during in-port maintenance and shortly before the crash.

The board said the cargo ship had other outages including about four minutes before the crash when electrical breakers unexpectedly tripped causing a loss of power to all shipboard lighting and most equipment when it was 1km from the bridge.

The Dali crew restored power, but another blackout occurred 300m from the bridge, which stopped all three steering pumps. The crew was unable to move the rudder to steer.

The report includes the first published investigative findings since the fully loaded container ship Dali caused the highway bridge to tumble into the Patapsco River. NTSB chair Jennifer Homendy will testify before a US House committee on Wednesday on the federal response to the collapse.

The report found no issues with the quality of the fuel onboard.