The National Highway Traffic Safety Administration (NHTSA) is opening a preliminary investigation into reports of fires in three Chevrolet Bolts.

According to the NHTSA, its Office of Defects Investigation (ODI) has received two complaints regarding a 2018 model year and a 2019 model year Chevrolet Bolt, with owners claiming their vehicles caught fire under the rear seat while parked and unattended. ODI conducted an investigation and also found a 2017 model year Bolt with a similar burn pattern in the rear seat area.

In all three cases, fire damage appeared to be concentrated in the battery compartment area “with penetration into the passenger compartment from under the rear seat.” One of the owners who encountered the issue reported smoke inhalation injuries.

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The NHTSA’s probe covers 77,842 Bolt EVs sold from the 2017 to 2020 model years.

The case involving smoke inhalation injuries was reported in a March 2019 incident in Belmont, Massachusetts when a Bolt caught fire in the driveway of its owner. The latter said the strong fumes from the car permeated the home during the three-hour fire, forcing them to have the house professionally cleaned. They also reported getting headaches from the smoke.

In a statement emailed to Reuters, GM said it is “cooperating with NHTSA in their investigation and we are conducting our own investigation into these complaints as well.”