Investigators have found traces of TNT on the French oil tanker that exploded in what authorities believe was a terrorist attack.
French Defense Minister Michele Alliot-Marie told the Associated Press on Friday said specialists from France, Yemen and the United States have been trying to determine what caused the Sunday blast and fire on the Limburg, which killed one crew member and spilled 90,000 barrels of oil into the Gulf of Aden.
The tanker Limburg, was towed into a northeastern Yemen port Friday. Investigators said metal and plastic pieces found on the deck suggested the ship was rammed by a smaller craft.
American officials said Sunday's blast was an act of terrorism most likely carried out by people with links to al-Qaeda, the terror network led by Osama bin Laden and blamed in the Sept. 11, 2001, attacks in the United States.
"It's become clear it's an act of terrorism," a U.S. intelligence official in Washington said Thursday on the condition of anonymity.
Oil markets appeared undisturbed Thursday by evidence the explosion was an attack, analysts 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.
French investigator Jean-Francois Perrouty told French television channel France 3 on Thursday that debris found on the deck of the tanker did not come from the tanker.
"We found on the Limburg deck some parts mainly made of plastic and of a mixed glass-resin material used for constructing yachts and, in Yemen, fishing boats. We found that on the tanker deck along with some metal debris," he said.
Yemen's minister of sea transport, though, said the parts might have come from the tanker's own life boat.
"Investigators have indeed found fiberglass parts but they might be from the tanker's rescue boat that was damaged in the accident. The parts will be sent to laboratories to be tested and determine whether it belonged to the damaged boat," Minister of Sea Transport Saeed Yafaei said Thursday, according to the official Yemen news agency Saba.
Earlier, a U.S. defense official said several factors pointed to a terrorist attack: the hole in the ship is at sea level and the vessel is 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.
The Limburg's captain earlier told AP that a crew member saw a fishing boat approach the tanker shortly before the blast.
At first, Yemen, which has been eager to emphasize its commitment to the U.S.-led war on terrorism, sought to dismiss reports that the blast was deliberate.
But a Yemeni government official, speaking on condition of anonymity, said the investigation so far has yielded contradictory information and the blast may have been an act of terrorism.
White House spokesman Ari Fleischer said Thursday, "We don't have any conclusions yet."