BMW is recalling nearly 30,000 plug-in hybrid vehicles in the United States.

Owners of affected vehicles are advised to park outside, as there is an increased risk of fire.

That said, the high-voltage battery is not the culprit.

BMW is recalling 29,119 plug-in hybrid vehicles sold in the United States, advising owners to park them outside because there’s a fire risk. Despite this recall targeting PHEVs specifically, the cars’ high-voltage batteries are not the issue.

Instead, an issue with the combustion engine’s starter has prompted the German automaker to recall certain 3 Series, 5 Series, and 7 Series models sold stateside. According to official documents submitted to the National Highway Traffic Safety Administration, water can get inside the starter’s electrical relay and, over time, lead to corrosion. Corrosion could affect the electrical connection within the relay and the ability to start the gas engine.