The National Transportation Safety Board (NTSB) said that a single loose wire on the 984-foot-long container ship MV Dali caused an electrical blackout that led to the 10,000 TEU ship veering and contacting the nearby Francis Scott Key Bridge in Baltimore, Maryland, which then collapsed, killing six highway workers. 

On March 26, 2024, at about 0129 local time, the 984-foot-long Singapore-flagged container ship MV Dali was transiting out of Baltimore Harbor when it experienced losses of electrical power, propulsion, and steering.. The ship struck Pier 17, the southern pier that supported the central span of the Francis Scott Key Bridge.

Investigators found that the pilots and the bridge team attempted to change the vessel’s trajectory, but the loss of propulsion so close to the bridge rendered their actions ineffective. A substantial portion of the bridge subsequently collapsed into the river, and portions of the pier, deck, and truss spans collapsed onto the vessel’s bow and forward-most container bays.

NTSB investigators traced the blackout to a single wire with a misplaced label, which created a precarious electrical connection that allowed the wire to disconnect from its terminal block, plunging the ship into darkness. Investigators found that wire-label banding prevented the wire from being fully inserted into a terminal block spring-clamp gate, causing an inadequate connection. There were thousands of wires on the Dali, and one loose wire would not have been easily found by the crew.

”Our investigators routinely accomplish the impossible, and this investigation is no different,’ said NTSB Chairwoman Jennifer Homendy. “The Dali, at almost 1,000 feet, is as long as the Eiffel Tower is high, with miles of wiring and thousands of electrical connections. Finding this single wire was like hunting for a loose rivet on the Eiffel Tower.

“But like all of the accidents we investigate, this was preventable,” Homendy said. “Implementing NTSB recommendations in this investigation will prevent similar tragedies in the future.”

As a result of the investigation, the NTSB issued new safety recommendations to the US Coast Guard; US Federal Highway Administration; the American Association of State Highway and Transportation Officials; the Nippon Kaiji Kyokai (ClassNK); the American National Standards Institute; the American National Standards Institute Accredited Standards Committee on Safety in Construction and Demolitions Operations A10; HD Hyundai Heavy Industries; Synergy Marine Pte. Ltd; and WAGO Corporation, the electrical component manufacturer, and multiple bridge owners across the nation.

A synopsis of actions taken Tuesday, including the probable cause, findings, and recommendations, can be found on ntsb.gov​. The complete investigation report will be released in the coming weeks.  

Thanks to Larry Witmer for contributing to this post.