Investigators have ruled out sabotage or terrorism as the cause of last week's giant fire at an oil refinery and storage facility near San Juan, the FBI special agent in charge in Puerto Rico said Friday.

"It was not terrorism or sabotage," Luis Fraticelli told a press conference at the Fortaleza, seat of the island's government.

He said the explosion and subsequent blaze at Caribbean Petroleum Corp.'s Bayamon refinery in the San Juan suburb of Cataño was caused by a fuel spill.

Fuel that escaped as one of the storage tanks was being filled found its way into a drain connected to a water-treatment plant, where gases accumulated and were ignited by a spark, he said.

Fraticelli said that while investigators are still trying to pin down the source of the spark, no trace of explosives was found in the refinery.

Marcial Felix, who heads the Puerto Rico office of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, said nearly 250 FBI and ATF agents were assigned to the investigation.

He said that though sabotage has been ruled out, negligence may have been a factor in the fire.

Speaking for the administration of Puerto Rico Gov. Luis Fortuño, Marcos Rodriguez-Ema said that if negligence is established, the government will do everything possible to recoup from Caribbean Petroleum the costs generated by the disaster.

"All the damage will be compensated for," he said, adding that addressing possible environmental problems would be the first priority.

Residents throughout San Juan were wakened in the wee hours of last Friday by the explosion at the refinery and two people were injured in the ensuing blaze, which took two days to put out.

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