FORT MYERS, Fla. — More than 3,500 rental cars were damaged or destroyed in a fire that burned near a Florida airport before being contained late Friday.

The Fort Myers News-Press reports the cars were in a grassy area used as an overflow lot by car rental companies that service Southwest Florida International Airport. The vehicles weren’t occupied.

Witnesses said they heard multiple small explosions and flames leaping high into the air as the flames spread across the area. Another 3,850 vehicles were undamaged, according to airport spokeswoman Vicki Moreland.

Investigators are trying to determine the cause of the fire.