Ford is urging owners of 2021 Ford Expeditions and Lincoln Navigators to park their vehicles outside and away from any structures due to a fire risk, the National Highway Traffic Safety Administration said Thursday.

According to the recall documents, more than 39,000 Ford Expeditions and Lincoln Navigators have a defect that causes risk of “underhood fire, including while the vehicle is parked and off.”

More than 32,700 of the affected vehicles are Expeditions and over 6,300 are Lincoln Navigators. The vehicles were built between December of 2020 and April of 2021, according to a statement from Ford.

“Until further notice, owners of these affected vehicles should not park them inside – they should only be parked outside and away from homes and other structures,” the NHTSA said in a Thursday press release. “Fires have occurred in vehicles that were parked and turned off.”

Ford said it has confirmed 16 fires related to the defect. Twelve of those happened when the vehicle was off and parked, one happened while the SUV was parked and on and three of the fires happened while the car was in motion, according to Ford’s statement. Fourteen of the fires happened in rental cars. The automaker said it is aware of one injury from the defect.

Ford does not know the cause of the fire risk and at this time has no way to fix the defect. However, Ford said it is treating the issue with a “high sense of urgency” and is working to inform customers who have vehicles that may be affected.

“We are working around-the-clock to determine the root cause of this issue and subsequent remedy so that customers can continue to enjoy using their vehicles” Jeffrey Marentic, the general manager of Ford Passenger Vehicles, said in a statement. “We recognize the importance of staying in touch with our customers until we resolve this matter.”

Drivers can check to see if their vehicle is part of the recall by entering the car’s Vehicle Identification Number (VIN) at NHTSA.gov/recalls.