The U.S. National Transportation Safety Board (NTSB) has identified a loose electrical wire as the root cause of the catastrophic allision involving the MV DALI and the Francis Scott Key Bridge.

According to the NTSB’s findings, the problem originated from wire 381 inside Terminal Block 1 on the ship’s main switchboard. Investigators discovered that an identification label had been positioned too close to the tip of the wire, preventing the bare end from fully inserting into the spring-grip terminal. As a result, the wire was never firmly clamped in place.

Over time, normal vessel vibrations caused the improperly seated wire to loosen further. In the early hours of March 26, 2024, the wire lost contact completely, triggering an electrical fault that shut down the ship’s auxiliary systems. This led to a sudden loss of propulsion and steering, leaving the DALI unable to maneuver as it drifted toward the Francis Scott Key Bridge.

The vessel ultimately struck a bridge pier, causing the structure to collapse and resulting in six fatalities.

The NTSB emphasized that the disaster stemmed from a simple but overlooked installation error, compounded by missed opportunities to detect the defect during assembly and maintenance checks.

Industry experts note that the incident underscores the importance of rigorous electrical installation standards, proper labeling practices, and thorough verification during routine inspections. The findings serve as a strong reminder that even minor technical oversights can escalate into large-scale maritime casualties.