A malfunctioning signal wire led to a blackout, causing the cargo ship Dali to crash into Baltimore’s Francis Scott Key Bridge, according to the National Transportation Safety Board (NTSB). The board criticized the Maryland Transportation Authority (MDTA) for not evaluating the bridge’s resilience to ship impacts.

The bridge collapsed on March 26, 2024, when the container ship Dali lost power and hit a support pier, resulting in the bridge spans plummeting into the Patapsco River.

The NTSB’s conclusive report revealed that a single improperly installed wire caused total power failure, leaving the Dali without propulsion or steering just before the crash. The board noted that the disaster might have been avoided if Maryland had implemented safety recommendations given years prior.

“The National Transportation Safety Board concludes that the likely cause of the container ship Dali’s collision with the Francis Scott Key Bridge was an electrical power outage due to a loose signal wire connection to a terminal block, resulting from incorrect installation of wireless label banding,” the board stated.

The container ship Dali remains amidst the wreckage of the Francis Scott Key Bridge nearly a week after it struck a structural pier, causing the bridge to collapse. (Jerry Jackson/The Baltimore Sun/Tribune News Service/Getty Images)

Investigators said the crew reacted quickly to the blackout but had too little time to restore power before the vessel struck the bridge. The ship’s proximity to the span, combined with delays in restarting its systems, made the collision unavoidable.

The report also faulted the MDTA for not conducting a vulnerability assessment, a step recommended by the American Association of State Highway and Transportation Officials to identify ways to protect bridges from ship strikes.

The NTSB said contributing to the collapse “was the lack of countermeasures to reduce the bridge’s vulnerability to collapse due to impact by oceangoing vessels, which could have been implemented if a vulnerability assessment had been conducted.”

Part of a span of the collapsed Francis Scott Key Bridge is suspended on the container ship Dali in Baltimore, Maryland, U.S., March 26, 2024. U.S. (Army Corps of Engineers/Handout via Reuters)

Engineers testified that the Dali’s crew misused a flushing pump as a service pump, a practice the ship’s operator, Synergy Marine Group, failed to detect or stop. That misuse limited the vessel’s ability to recover power after the blackout.

The NTSB also criticized Synergy for allowing critical electrical systems to run in manual mode rather than automatic, which hindered the Dali’s recovery after the power failure.

“Staff found that Synergy operational oversight was inadequate because it did not discontinue crew’s ongoing use of the flushing pump as a service pump for the diesel generators aboard the Dali, and at least one other vessel,” NTSB engineer Bart Barnum said.

Part of the collapsed bridge on top of a cargo ship. (FBI Baltimore)

The board also found that communication failures prevented timely warnings to highway workers, who had no chance to evacuate before the bridge collapsed.

The NTSB’s findings came a day after Maryland officials said rebuilding the Francis Scott Key Bridge will take two years longer than expected and cost more than twice the original estimate. State engineers now say the project won’t be finished until 2030 and could cost as much as $5.2 billion — up from the initial $1.9 billion projection used to secure federal funding.

Jim Harkness, the MDTA’s chief engineer, told The Washington Post that inflation and market factors are driving the increase.

“Estimating is difficult on these larger projects,” he said. “The market factors, that all comes into play.” Transportation Secretary Sean Duffy had predicted in August that the final bill would be “double plus” the initial estimate once federal dollars were committed.

The NTSB’s findings paint a picture of cascading failures — from a single faulty wire to years of missed safety precautions — that combined to cause one of the deadliest infrastructure disasters in Maryland’s history.

As the state works to rebuild the bridge, the growing costs and timeline delays underscore how deeply the collapse continues to ripple through Maryland’s economy and infrastructure.