Hatfield said the Bahamas —where the ship is registered, or flagged — is leading the investigation, with the Coast Guard and National Transportation Safety Board leading U.S. interests in the probe.
She said investigators have been with the ship since it arrived Thursday in Mobile. Since then, she said, interviews have been conducted with passengers and crew and forensic analysis has been performed on the ship.
She said the crew responded appropriately to the fire. "They did a very good job," she said.
In an email after Monday's 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 Triumph left Galveston, Texas, on Feb. 7 for a four-day trip to Mexico. The fire paralyzed the ship early Feb. 10, leaving it adrift in the Gulf of Mexico until tugboats towed it to Mobile. Passengers described harsh conditions on board: overflowing toilets, long lines for food, foul odors and tent cities for sleeping on deck.
Hatfield said investigators from the Coast Guard and NTSB would stay with the ship until about the end of the week, then continue work at their respective offices. She said the investigation will look further at the cause of the fire and the crew's response, as well as why the ship was disabled so long.