Two electrical blackouts on the Dali freighter sent members of its crew and the pilots on board scrambling to control the vessel as it approached the Francis Scott Key Bridge in the early morning hours of March 26.

Their efforts — which would prove unsuccessful — are laid out in detail in a preliminary report released Tuesday by the National Transportation Safety Board.

The 984-foot container ship struck the bridge just before 1:30 a.m. March 26, collapsing much of the 1.6-mile span into the Patapsco River and killing six construction workers who were repairing potholes.

The preliminary report offers no conclusions or likely causes, but does present a minute-by-minute — sometimes second-by-second — account, including key radio broadcasts and actions like the Maryland Transportation Authority Police swiftly shutting down bridge traffic.

Here’s how federal investigators say things played out:

Afternoon, March 25: About 10 hours before its departure from the Port of Baltimore, the Dali experiences two electrical blackouts during in-port maintenance. In the first, a crew member mistakenly closes an exhaust damper, stalling the engine. A second blackout occurs when insufficient fuel pressure slows a generator.

12 a.m. March 26: Seven construction workers, accompanied by one inspector, repair potholes in the southbound lanes of the Key Bridge. Maryland Transportation Authority Police units are stationed at either end of the bridge.

12:05 a.m.: A senior pilot and an apprentice pilot, both with the Association of Maryland Pilots, board the Dali. The captain reports to the pilot that the ship is in “good working order,” according to NTSB investigators.

12:36 a.m.: The Dali is pulled away from a dock in the Port of Baltimore by two tugboats, the Bridget McAllister and the Eric McAllister.

1:07 a.m.: The Dali enters the Fort McHenry Channel and, around the same time, the senior pilot gives orders for the tugboats to depart, as is “normal practice,” according to the NTSB. The senior pilot turns over control to the apprentice pilot.

1:09 a.m.: The vessel’s speed is increased from “dead slow ahead” to “slow ahead.”

1:25 a.m.: The first blackout occurs, about 0.6 miles away from the Key Bridge — or, as the NTSB noted, three ship lengths. The Dali experiences a loss of electrical power to its lighting and most equipment, resulting in its propeller stopping along with its three steering pumps, which means the rudder cannot be moved.

1:26 a.m.: The apprentice pilot calls the pilot dispatcher by cellphone as the senior pilot takes control. The pilots call for assistance from a tugboat; the Eric McAllister, 3 miles away, immediately heads that way, but doesn’t reach the Dali in time. After an emergency generator starts, restoring partial power to the rudder, the senior pilot orders the vessel turned 20 degrees to the left.

1:27:01 a.m.: The pilot dispatcher tells the Maryland Transportation Authority Police’s duty officer that the ship lost power, and then informs the Coast Guard. At the same time, the senior pilot orders an anchor to be dropped and the crew begins to do so. The Dali suffers a second electrical blackout, this time about 0.2 miles from the bridge.

1:27:23 a.m.: The pilot orders a sharper turn to the left, but the main engine is shut down and there is no propulsion to power the maneuver.

1:27:25 a.m.: A pilot issues a warning to other boats over a very high frequency (VHF) marine radio.

1:27:32 a.m.: The crew manually closes breakers, regaining electrical power for the ship but not propulsion.

1:27:53 a.m.: The duty officer with the Maryland Transportation Authority Police orders the police officers at either end of the Key Bridge to close it to traffic.

1:29:10 a.m.: The Dali strikes the southern pier supporting the central span of the Key Bridge, sending it tumbling into the Patapsco River along with seven construction workers. A Dali crew member told investigators that the ship struck the bridge as he was releasing the brake on the port anchor, and he had to run to escape pieces of the bridge falling on the bow. Another crew member is injured escaping debris. A road maintenance inspector on the bridge is able to run to safety by reaching a span of the bridge that didn’t collapse.

1:34 a.m.: The Coast Guard issues urgent notice, requesting assistance.

1:51 a.m.: The first Coast Guard boats arrive on the scene.

1:55 a.m.: A construction worker, who fell from the bridge in his truck but escaped the vehicle, is rescued by a Maryland Transportation Authority Police boat.

The search for the other workers continued through the day before efforts shifted to recovery. All six bodies have now been recovered with the last found last week.

Authorities also have been removing the bridge wreckage from the shipping channel and, on Monday, used explosives to cut the bridge trestle draped across the bow of the Dali as part of the effort to refloat the grounded ship.