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.

Ford said in U.S. government documents posted Thursday that it doesn’t know what’s causing fires in some 2021 Ford Expedition and Lincoln Navigator SUVs.

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

The automaker also is recalling 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.