HOUSTON -- Carnival Cruise Lines has canceled a dozen more planned voyages aboard the Triumph and acknowledged that the crippled ship had been plagued by other mechanical problems in the weeks before an engine-room fire left it powerless in the Gulf of Mexico.The company made the announcement Wednesday as the Triumph was being towed to a port in Mobile, Ala., with more than 4,000 people on board, some of whom have complained to relatives that conditions on the ship are dismal and that they have limited access to food and bathrooms.The ship will be idle through April. Two other cruises were called off shortly after Sunday's fire.Debbi Smedley, a passenger on a recent Triumph cruise, said the ship had trouble Jan. 28 as it was preparing to leave Galveston. Hours before the scheduled departure time, she received an email from Carnival saying the vessel would leave late because of a propulsion problem.The ship did not sail until after 8 p.m., she said."My mother is a cruise travel agent so this is not my first rodeo. I have sailed many, many cruises, many, many cruise lines. This was, by far, I have to say, the worst," said Smedley, of Plano.After losing power on its most recent journey, the ship drifted until Tuesday, when two tugboats began moving it toward shore. A third tugboat was en route Wednesday from Louisiana.The National Transportation Safety Board has opened an investigation of the fire.