The investigation of the incident and the crew's response to the fire will last about six months, Lt. Cmdr. Teresa Hatfield, the Coast Guard's Marine Casualty Investigation team leader, said during a conference call Monday.
In an email after the conference call, Coast Guard spokesman Carlos Diaz described the oil return line that leaked as stretching from the ship's No. 6 engine to the fuel tank, The Washington Post reported.
"We know that the fire originated in front of a generator. You can see the ignition marks on the wall," said Patrick Cuty, a senior marine investigator of the U.S. Coast Guard of the fire that left the massive ship adrift in the Gulf of Mexico last week.
Cuty said the site of the fire had three generators with three more in a second engine room not involved in the fire.
The ship had a problem on an earlier cruise with its propulsion system, CNN reported Monday.
"We'll know by the end of the next week whether the generator is the same one that was having an issue, an anomaly, in January," Cuty added.
It could take up to a year to determine the cause of the fire, with analysis of the ship's records, wiring and automated data, CNN said.
The Carnival Triumph was on the third day of a four-day cruise from Galveston, Texas, to Mexico, carrying 3,100 passengers and 1,200 crew, when the fire brought the trip to a halt. The loss of power stopped the ship and caused failures in its sewage and cooling systems. The ship is undergoing repairs in Mobile, Ala.