An April fire at a rental lot at the Southwest Florida International Airport has been ruled an accident.

The 15-acre fire destroyed nearly 4,000 vehicles and resulted in $100 million in damages. About 2,500 of the vehicles were from Enterprise and Avis. More than 1,000 destroyed vehicles were from Hertz. 

Officials believe the fire was probably started by hot exhaust over dried grass.

Fire investigator Lee Quick provided his report to Auto Rental News. The report concludes:

"After my examination of the fire scene, examination of physical evidence, knowledge of fire development, witness information, and supporting documents and environmental conditions, I determined the fire originated near ground level. This was likely caused by a hot exhaust system contacting dry grass underneath a vehicle. Once the fire started, surrounding combustible items would have ignited with available oxygen and allowed the fire to spread rapidly onto the surrounding grasses and vehicles. I am classifying this fire as Accidental."