ST. AUGUSTINE, Fla. -

A major fire continues to burn after an explosion at a St. Augustine gas station just before 5 p.m. Friday.

State Road 16 remains closed in both directions as firefighters battle the blaze at the BP station hear Masters Drive.

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Authorities said a fuel delivery was being made at the gas station when the explosion occurred. Residents

"They had these couple-thousand gallon tanks that were actually on the side, kind of a substation of the gas station," witness Brian High said. "A fuel truck was over there, and the whole thing exploded."

Officials confirmed that one person was treated and transported to Shands Jacksonville Medical Center, but that person's identity was not known.

Residents told Channel 4 that an explosion could be heard 5 miles from the gas station. Black smoke from the blaze not far from the St. Augustine Airport and was visible from Clay County, 25 miles to the west.

"The fire spread rapidly to the buildings that were on that site," St. Johns County fire spokesman Jeremy Robshaw said. "We have a large petroleum fire of some sort -- some type of flammable liquid is burning."

The Sheriff's Office initially asked residents within one-half mile of the fire to leave the area for their own safety, but that was lifted about 45 minute later. Only people who live in the immediate area are still being kept away from their homes.

About 6:30 p.m., the black smoke turned to white, indicating firefighters making progress on the fire. They expected to continue battling the fire into the evening and roads in the area may be closed for hours.

St. Johns County Sheriff's Office Sgt. Chuck Mulligan said the fire was contained to the property of the gas station, but the buildings are heavily damaged, possibly destroyed.