ATLANTA — Now that investigators have determined the origins of the engine-room fire that paralyzed a Carnival cruise ship at sea for five days, they will try to learn more about the cause, the crew's response, and why the ship was disabled for so long.

A Coast Guard official said Monday that a leak in a fuel oil return line caused the engine-room fire that disabled the Carnival Triumph in the Gulf of Mexico, leaving 4,200 people without power or working toilets for five days.

Cmdr. Teresa Hatfield addressed the finding in a conference call with reporters. She estimated that the investigation of the disabled ship would take six months.