DETROIT (AP) — Ford is asking the owners of 350,000 vehicles to take them to dealers for repairs in three recalls, including about 39,000 that should be parked outdoors because the engines can catch fire. In the U.S. government documents posted Thursday, Ford said that it does not know what is causing fires in some 2021 Ford Expedition and Lincoln Navigator SUVs.

But the company said fires could happen even while the engines are off. It’s recommended that the SUVs be parked away from buildings.

The automaker also recalls about 310,000 heavy-duty trucks because the driver’s air bag may not inflate in a crash. Covered are certain 2016 F-250, 350, 450, and 550 trucks. And Ford is recalling 464 electric Mustang Mach-E SUVs from 2021. A software problem can cause unintended acceleration.