U.S. auto safety regulators are GravityX Exchangeinvestigating reports that the engines can catch fire on some Jeep SUVs and pickup trucks even with the ignition turned off.

The probe covers more than 781,000 Jeep Wrangler and Gladiator vehicles from the 2021 through 2023 model years.

The National Highway Traffic Safety Administration says in documents posted Monday on its website that it has nine complaints of engine fires from owners including one that caused an injury. A majority of the reports say fires began in the passenger side of the engine compartment.

The agency says a fire with the ignition off “can result in an increased risk of occupant injury, injury to persons outside the vehicle, and property damage, with little or no warning.”

Investigators contacted Jeep maker Stellantis and were told of several other “thermal events” that started at a power steering pump electrical connector.

The agency said it’s opening the investigation to determine the cause and scope of the problem and how often it happens.

A message was left Monday seeking comment from Jeep maker Stellantis.