View of the Dali cargo vessel which crashed into the Francis Scott Key Bridge causing it to collapse in Baltimore, Maryland, U.S., April 4, 2024. REUTERS/Nathan Howard

By David Shepardson

WASHINGTON (Reuters) -The National Transportation Safety Board will hold a public hearing on Tuesday to determine the probable cause of the March 2024 collapse of Baltimore's Francis Scott Key Bridge that was struck by the cargo ship Dali, killing six people.

The incident prompted the board to call for urgent safety assessments of 68 bridges in 19 states including iconic crossings like the Golden Gate Bridge, Chesapeake Bay Bridge, Brooklyn Bridge and George Washington Bridge. The review focuses on bridges built before 1991 and frequented by ocean-going vessels that have not undergone vulnerability assessments.

The crash of a Mexican Navy training ship into the Brooklyn Bridge in May also raised concerns about risks to bridges from vessels.

One key question is why the Dali lost electrical power several times before the crash into the Key Bridge, including experiencing a blackout during in-port maintenance and shortly before the crash.

Power outages happen at sea and the NTSB has been considering new recommendations to prevent catastrophic collisions.

The NTSB said last year the Dali 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 0.6 mile (1 km) from the bridge.

A replacement bridge was initially estimated to cost $1.7 billion to $1.9 billion and be completed by late 2028. On Monday, state officials said they now expect the bridge will cost $4.3 billion to $5.2 billion and open to traffic only in late 2030. They cited a new pier protection system and a new longer, higher design as reasons for the increased costs.

"We remain committed to rebuilding as safely, quickly, and efficiently as possible," Maryland Governor Wes Moore said, expressing disappointment at the longer rebuilding schedule.

In September, U.S. Transportation Secretary Sean Duffy raised concerns about the project cost.

In April 2024, the FBI opened a criminal probe into the collapse.

(Reporting by David Shepardson; Editing by Lincoln Feast.)