New York (CNN) -- Investigators know roughly where the flames erupted in the engine room of the Carnival Triumph, but it could be a year before they learn what caused the fire, which left the massive ship adrift for days in the Gulf of Mexico.
"We know that the fire originated in front of a generator," Patrick Cuty, a senior marine investigator for the U.S. Coast Guard, told CNN on Sunday.
"You can see the ignition marks on the wall."
There are three generators in the engine room where the fire broke out. Three other generators are in a second engine room that wasn't involved in the fire, Cuty said.
The same ship encountered a problem in January with its propulsion system, according to a notice posted on the website of Carnival senior cruise director John Heald.
"We'll know by end of the next week whether the generator is the same one that was having an issue, an anomaly, in January, according to passengers we interviewed from previous cruises," Cuty said.
It could take up to a year to determine the cause of the fire, however, because of the amount of work involved. It includes a painstaking analysis of the ship's records, automated data and wiring.
The Triumph was on the third day of a planned four-day cruise from Galveston, Texas, to Mexico when the fire broke out and brought the trip to a halt. It was carrying more than 4,200 people, including 3,100 passengers.
The loss of power not only crippled the ship but also created smelly conditions. Toilets stopped working, and waste spilled onto floors and into hallways. Passengers had to use plastic bags to collect their waste.
Passenger Cassie Terry described the ship as "a floating toilet, a floating Petri dish, a floating hell" in a lawsuit filed Friday against Carnival for unspecified damages related to the cruise.
Passengers reported long lines for food, shortages of fresh water and widespread boredom. Many passengers slept in hallways or outside to escape the odors and heat below decks.
The Triumph was eventually towed into port in Mobile, Alabama, Thursday night, and the last passengers disembarked Friday. The ship is at a Mobile shipyard for repair and won't resume cruises until at least mid-April.
Cuty's team remains on board the ship cataloging the location of everything in the engine room where the fire started. He said investigators are still working on lighting the room because the ship is operating on temporary power from a generator on the dock.
It's likely that Carnival will make repairs on the ship in Mobile, where the investigation is taking place, Cuty said. However, a Carnival spokesman says no decision has been made on a schedule or location for repairs.
On Saturday, Carnival crew members were bused to and from the ship to help with the clean up. One housekeeper told CNN it wasn't pleasant work but said it had to be done, and the crew was willing to do it.
Passengers have praised the crew for its response during the ordeal.
Sewage, gray water and all waste generated during a cruise are stored in tanks and removed at the end of each trip, according to Cuty.
Because the Carnival Triumph is a Bahamian-flagged vessel, the Bahamas Maritime Authority is the primary investigative agency and will work with the Coast Guard and the National Transportation Safety Board.
Investigators pulled the voyage data recorder, a device that records alarms, voice communications on the bridge, engine speed, navigation information and rudder angle, Cuty said.
It appears that the fire suppression worked as designed, Cuty said Friday. The engineer who was on watch around dawn February 10 saw the fire ignite over a video feed and immediately notified the bridge, Cuty said.
Based on an inspection of the engine room Thursday, Cuty said the fire did not appear to have been large.
As compensation, Carnival offered each passenger $500, a free flight home, a full refund for the trip and for most expenses incurred onboard, and credit for another cruise.
Susan Candiotti and Ross Levitt, CNN