A state of emergency has been declared in San Juan
Officials in Puerto Rico have ordered the evacuation of a whole neighbourhood near the capital after an explosion at an oil refinery triggered a major fire.
The blast at an oil refinery near San Juan, was measured to a strength of a 2.8-magnitude quake.
Puerto Rico's governor declared a state of emergency in the capital and four nearby towns, moving 1,500 people.
No-one was killed but hours after it began on Friday, fire-fighters were struggling to dampen the flames.
Two people at a nearby US army base were injured.
Some 130 fire-fighters, supported by the National Guard, tackled the fire which at its peak saw flames reach 100ft (30m) above the oil centre.
The US aviation authority diverted plane traffic from the area due to the billowing black smoke and some prisoners in a high security facility were moved across the island.
The fire, at the facility owned by the Caribbean Petroleum Corp, first destroyed 11 tanks before spreading to others containing flammables such as jet fuel, bunker fuel and petrol.
"There are 17 tanks ablaze, and fire-fighters are cooling the rest to avoid their explosion," Governor Luis Fortuno said.
Residents were advised to remain indoors to avoid the thick black smoke set off by the fires.
Officials said they did not know what had caused the explosion. The FBI was reported to be helping the authorities in their investigations.
One of the first fire-fighters to arrive on the scene described it as an "inferno".
Resident Tamara Rivera, 37, told Reuters she initially believed an earthquake had struck.
"But when I went outside, I saw the big orange glow. It looked like daylight over there," she said.
Puerto Rico is the US self-governing commonwealth in the Caribbean.