The fire began just after 5am on 29 November in a rental car overflow car park at Nantucket airport.
By the time emergency responders arrived, the blaze had engulfed five SUVs and come within 40 feet of airport fuel tanks.
The Nantucket Current was first to report that the five Hertz-owned late model SUVs had been returned to the airport by Secret Service members less than 24 hours earlier.
The security detail had been protecting President Joe Biden during his annual Thanksgiving weekend holiday.
News of the fire spread fast — fuelling conspiracy theories about might have been the cause.
Nantucket Fire Department chief Michael Cranson, who was inundated with media inquiries, told the Current that the fire was not suspicious.
Investigators are focusing on a Ford Expedition vehicle that had been subject to a safety recall.
Hertz, who rented the vehicles to the Secret Service, told The Independent in a statement they were assisting authorities with the investigation.
No one was injured in the fire.