Al Mukalla, Yemen ? A fiery explosion aboard a French oil tanker in the Arabian Sea resulted from an attack on the ship, U.S. and French officials concluded Thursday. The Americans said it was an act of terrorism most likely carried out by people with links to al-Qaida.

Investigators from France, Yemen and the United States had been trying to determine what caused Sunday’s blaze on the Limburg that killed one crew member and sent 90,000 barrels of oil pouring into the Gulf of Aden.

“It’s become clear it’s an act of terrorism,” a U.S. intelligence official in Washington said on the condition of anonymity.

Al-Qaida would consider an oil tanker an economic target, the official said. Recent statements from al-Qaida leaders have suggested attacks on economic targets are imminent.

The attack bears a number of similarities to the suicide boat strike on the USS Cole in October 2000, the official said.

France’s Foreign Ministry also said the ship had been attacked.

“The initial results of the inquiry carried out by French, Yemeni and American investigators suggest the explosion Oct. 6 on board the French oil tanker, the Limburg, was due to an attack,” a statement said.

Earlier, a U.S. defense official said several factors pointed to a terrorist attack: the hole in the ship was at sea level, which is consistent with it being struck by a boat or weapon, and the vessel was relatively new, making it unlikely that a malfunction caused the blast.

U.S. intelligence also picked up indications in recent weeks that terrorist groups remain interested in targeting maritime shipping, the defense official said.

Speculation that the incident was an act of terrorism arose shortly after the explosion, which spilled oil along 45 miles of coastline. The Limburg’s captain later said a crew member saw a fishing boat approach the tanker shortly before the blast.

The United States has sent a team of Navy investigators.