(NewsNation) — A preliminary National Transportation Safety Board report detailed the events leading up to a collision between a cargo ship and a Baltimore bridge that shut down the port of Baltimore and killed six construction workers.

The preliminary report laid out a timeline of events that occurred before the Dali struck the Francis Scott Key Bridge, noting that the ship lost power twice before impact, with crew members working to restore power both times.

While the Dali did regain power before the impact, the crew was unable to regain propulsion systems in time to avoid the bridge. The crew also called for an assist from a nearby tugboat, the Eric McAllister, to help steer it away from the bridge and begin the process of dropping anchor. The tug was unable to reach the Dali in time to avert the collision.

The report also found one of the two harbor pilots on board warned other ships in the area of the Dali’s struggles, and authorities also shot down traffic on both ends of the bridge, leaving only the construction crew and an inspector on the bridge at the time of impact.

The Dali, a Singapore-flagged ship, did lose power the day prior to the crash. The NTSB is still investigating the ship’s electrical systems and if there is any connection between the two events.

All members of the Dali’s crew and both harbor pilots, a senior pilot and an apprentice pilot, tested negative for drugs and alcohol. Testing also found no concerns with the fuel used in the ship.

The agency is still working to determine a probable cause of the crash and is looking into the Dali’s electrical and propulsion systems as well as impact mitigation efforts used on the bridge supports.

NTSB head Jennifer Homendy and other officials will be testifying in Congress on Wednesday regarding the collision.