The reason behind the loss of propulsion on the ferry MV Tacoma late last month is still a mystery, according to Washington State Ferry officials, but appears worse than originally imagined.

“The update on the Tacoma is that the tech reps that are there from Siemens Global have not completed their investigation,” Capt. George Capacci, Interim Assistant Secretary of Transportation, said Friday.

Workers from Siemens believe the damage is more extensive than the initial review indicated, and the company has been tasked with completing a repair plan for the troubled vessel.

“The damage was a little bit more than we had anticipated,” Capacci said. “We’re not there yet.”

Capacci said he expects to have more specifics “in the next couple of weeks.”

Even with Tacoma out of use, Capacci noted, the overall ferry system has been returned to nearly full-scale capacity and every route once again has the appropriate number of vessels in service.

“Some of them are a little below capacity, but there are the same amount of boats on every route as before,” he explained.

Capacci said that the initial decision to pull vessels from other routes to better serve the Bainbridge Island-Seattle run was a difficult one, but that he felt it was the right one.

“There are no easy choices,” Capacci said. “You’ve got to weigh the plusses and the minuses and do the best you can for the most.”

The Tacoma lost propulsion power just before 1 p.m. Tuesday, July 29 as it neared Bainbridge Island on the 12:20 p.m. sailing from Seattle. The vessel stopped just outside Eagle Harbor and set anchor to avoid becoming beached; it was just the second time in 40 years that a state ferry was forced to drop anchor.

The ferry MV Sealth from Bremerton was diverted from its route to pull the Tacoma away from the shore, and two tugboats were called to the scene to guide the disabled ferry back to the Bainbridge terminal.

The temporary and unexpected loss of Tacoma, which occurred simultaneously to several other vessels being taken out of rotation for routine maintenance, was described by Capacci as “unprecedented.”

Capacci also noted Friday that WSF has launched an internal Board of Inquiry “to investigate the root causes of the power failure, determine contributing factors, and make recommendations to prevent this type of event in the future.”