- [Narrator] In the early hours of Tuesday, March 26th, 2024, the container ship Dali smashed into and destroyed the Francis Scott Key Bridge in Baltimore.

The National Transportation Safety Board's lead investigator, Marcel Muise, has been working to find out what caused the Dali to lose power.

His team has now released preliminary reports that suggest how a series of unfortunate events may have led to this tragedy.

- Ships are complicated.

They need electrical power to run a variety of systems, including propulsion, and steering, and navigation.

- [Narrator] The investigation reveals that, on the night of the crash, the Dali was running two of its four power generators.

(electricity buzzing) (intriguing dramatic music) Together, they produce over eight megawatts of electricity to power nearly everything on the ship, including the fuel and water pumps for the main engine, and the hydraulics of the steering mechanism.

- Ships generate a great deal of electricity to run.

And much like your own house where you have circuit breakers to ensure that if there is a disruption or a problem, they'll trip, ships have them too.

- [Narrator] The investigation discovers a loose cable, (electricity buzzing) (dramatic ominous music) which lawsuits claim was shaken loose by engine vibrations, causing a power surge that tripped two breakers, (breaker clacking) disrupting the electrical power supply.

The system should have automatically switched to a secondary circuit, but lawsuits alleged the control was set to manual, so did not automatically switch, causing a blackout across large parts of the ship.

The pumps required to run the main engine and the steering all shut down, which killed the propulsion and locked the rudder in place.

A small emergency generator kicked in, and the crew closed the trip breakers, but the engine was still offline.

- When the ship goes dark, the main propulsion engine of the ship also cuts off.

It's not getting the fuel, the lube oil, the water.

You basically have stalled that engine.

- [Narrator] But before the crew had a chance to restart the engine, there was a second blackout.

Investigators discovered that the generators caused this outage.

One lawsuit claims that, after the first blackout, the pump supplying the generators with fuel shut down.

And even when the power came back on, this pump did not restart automatically.

The generators would then have lacked fuel pressure, which could have caused them to run erratically, creating power fluctuations that tripped the breakers, (breakers clacking) and caused the ship to go dark again.

(buzzer buzzing) (electricity buzzing) (water murmuring) (wind whooshing)