Three sets of remains were found in the rubble of a gas station explosion in Rockbridge County, Virginia, state police said.

Matching the remains to identities could take several days, Virginia State Police Bureau of Criminal Investigation Sgt. Rick Garletts said in a statement Saturday afternoon.

The explosion at the fuel stop, called South River Market, was reported about 9:30 Saturday morning, and rescue crews have been combing through the rubble in an initial search for three to five people who might have been at the site before the blast.

Four injured in the explosion were taken to Carilion Stonewall Jackson Hospital hospital.

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State police opened a criminal investigation at the behest of local authorities. However, Garletts emphasized that every investigation by his bureau is a criminal inquiry until the facts prove otherwise.

State police initially said in a statement on the explosion, "At this time it does not appear suspicious in nature."

Neighbor Ryan Clark told NBC News affiliate WSLS of Roanoke, Virginia, that he saw fire after the blast.

"All you could see was probably an 80-foot tower of flame and smoke going everywhere and debris everywhere," he said. "And by the time I got to the tracks there, you could just see there's this utter devastation."