Washington State Ferry officials still aren’t sure what caused the ferry MV Tacoma to lose power during a sailing from Seattle to Bainbridge Island this week that left hundreds of passengers stranded in Puget Sound.

Capt. George Capacci, Interim Assistant Secretary of Transportation, said in a telephone press conference Friday that the unfortunate turn of events that completely shut down the system’s busiest route was one that had never been seen before.

“This is an unprecedented situation we find ourselves in,” Capacci said.

The loss of the 202-car-capacity Tacoma came as the ferry MV Wenatchee, a Jumbo Mark II-class boat that serves the Bainbridge route, is in dry dock in Canada for repairs.

This week’s ferry problems were further heightened when one of the state’s newest vessels was temporarily pulled from service on the Mukilteo-Clinton route.

Capacci said WSF will be past this week’s rough patch by the weekend, when ferries under repair are back in service.

“We’re hoping, anticipating that service will be restored Saturday,” he said. “We have a very fragile system. When one boat is out of the system, it’s very challenging. When four are out, it’s extremely challenging.”

The cause for the loss of propulsion aboard the Tacoma is still unknown.

“We’re still investigating the problem,” Capacci said, and added that WSF hopes to have a repair plan ready next week.

The Tacoma lost propulsion power just before 1 p.m. Tuesday 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; 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.

Onboard the stranded vessel, the general mood of the approximately 405 passengers was agreeable and unconcerned. Most of them were more interested than upset, with many crowding the decks with cameras and cell phones to document the towing efforts.

Alcohol and concession sales continued, although on a cash-only basis as the credit card reader failed during the initial power outage.

Also present on board, luckily, were at least two paramedics from Bainbridge Island Ambulance. Fortunately, their services were not required.

“I’m pretty impressed with how they got another ferry here,” said passenger Paul Faget of the arrival of Sealth. “That was pretty resourceful.”

Faget described himself as “a long-time commuter,” and said that he had never heard of such an occurrence on a Washington ferry.

“When they first announced it I thought, ‘This is going to take all day,’” Faget laughed, saying that he had planned to take yet another ferry ride later in the day to British Columbia.

“I’ve got a couple of hours to spare,” he admitted.

Fellow passenger James Farrenberg was less at ease about the delay, saying that he needed to be on the road already to Yakima to see to personal business.

“I left work early,” Farrenberg said. “I’ve been riding the ferry every day for 10 years. It had to be the trip I’m in a hurry.”

Upon the vessel’s eventual safe docking at Bainbridge at approximately 3 p.m., the crowd of passengers standing outside on the sun deck erupted into applause for the captain and crew.

Hearing the applause, Tacoma skipper Captain Ty Anderson emerged from the bridge onto the upper-most deck and waved triumphantly.

“We train real hard,” he told the passengers. “But this is the first time it’s ever happened.”

The Bainbridge Island-Seattle ferry route is the busiest in the state, and carried more than 6.2 million riders last year out of the system’s 22.5 million total ferry travelers.

Many on shore were happy to see the Tacoma finally arrive after a more than two-hour delay.

Travelers weary of their wait for a boat to Seattle gave out a collective hoot of approval when an announcement came over the terminal intercom that the ferry MV Tacoma was minutes away from docking.

Mechanical problems aboard the ferry — a crew member said the ship lost propulsion power as it approached Eagle Harbor — left the vessel dead in the water off Bainbridge just before 1 p.m. Tuesday.

James Melillo of Seattle stood at the edge of the upper end of the parking lot at the Bainbridge terminal, where a small gaggle of delayed passengers peeked through a clearing of trees to watch the two tugs push and pull the troubled Tacoma into the harbor. Two news helicopters from Seattle television stations hovered in the air above.

Melillo was on Bainbridge to visit a friend for a business lunch, and had been hoping to catch the 2:55 p.m. sailing back to Seattle.

“It’s confirmed why I live in Seattle and visit friends over here, versus the opposite. As I told my friend Scott Karren when he moved over here, I’m the only one of your friends that will be honest. I’m not going to visit you. All your friends will lie and say they will take the ferry,” Melillo said.

Once Karren got oysters, Melillo said he had changed his mind about visits to Bainbridge.

Then came Tuesday’s long wait for a ferry.

“I’ll never get him to visit again,” Karren said.

“We met for a business lunch, and now we’re trying to figure out what to do,” Karren recalled.

Melillo noted that they are both seasoned travelers.

“The reality is, we fly 150,000 miles a year, each. How could you run a business from Hooterville?” Melillo asked.

Maggie Rees, on a visit to Seattle from London in the United Kingdom, decided to hop aboard the ferry for a one-hour visit to Bainbridge.

She laughed when she recalled coming over earlier on the Tacoma.

“We wanted to take a trip around the bay,” Rees said.

The long wait to get back to Seattle would mean less time for sightseeing there, but Rees didn’t want to pass judgement on the ferry system because of Tuesday’s delays.

“It could be an isolated case for all I know,” she said.

Travelers waiting for a boat to Seattle sprawled out in the walk-on passenger walkway to the ferry, or stretched out on benches outside the ferry to soak up the sun. Others read books, jammed the nearby coffee stand or walked their children around the ferry terminal. And others simply gave up and left.

Abraham Neuwelt of Bainbridge Island and his fellow musicians Squid Samson and Shion Yamakawa had planned to board the

2:05 p.m. ferry so Samson could submit an application for a busker permit at the Pike Place Market.

When the boat never came, they instead pulled out their instruments and started playing to their fellow stranded passengers in the passenger walkway.

Review writer Luciano Marano contributed to this story.