Fire officials in the American Caribbean territory of Puerto Rico say a massive fire at a petroleum storage depot near the capital San Juan will take days to bring under control.
The explosion as eleven tanks blew up was so strong it created a 2.8 magnitude jolt on the Richter scale. The fireball spread to six more tanks containing jet fuel, bunker oil and gasoline.
Up to 2000 nearby residents were evacuated and people further away were warned to stay indoors as a huge column of black smoke reached hundreds of metres into the air.
Officials said they were also watching out for rain, which could mix with the smoke to create toxic rain.
Investigators meanwhile have found graffiti nearby including the spraypainted words "boom", "fire" and "R.I.P".
Police superintendent Jose Figuera Sancha says they are investigating whether the explosion was sabotage.