A ferry carrying hundreds of passengers on the Washington State Ferries' busiest route has lost power.

Ferries spokeswoman Marta Coursey says the Tacoma was on the Seattle-to-Bainbridge-Island run when it lost propulsion Tuesday afternoon.

She says the vessel, carrying 405 passengers and 138 cars, has dropped anchor and is stable in the water off Bainbridge Island, west of Seattle.

Coursey says tug boats have been dispatched to tow the Tacoma to shore. Another ferry that was on the Bremerton-to-Seattle run, the Sealth, was rerouted to be on standby status next to the Tacoma.

The Washington State Ferries system operates the largest ferry fleet in the United States, carrying about 23 million passengers each year.