A Toyota Prius recall was issued this week as the hybrid vehicles may have a flaw with their design that could pose a fire risk.

The carmaker said on Wednesday that the safety recall affects more than 1 million of its Prius plug-in hybrids and C-HR SUV models. The vehicles have a problem with their electrical systems that could result in fires at times if not fixed.

Toyota said that the problem has to do with the cars’ wire harnesses that connects to their power control units as these can wear away over time, generating heat and potentially igniting. More than half of the affected vehicles were in Japan, while just under 200,000 of them are in the U.S.

The rest of the vehicles covered in the Toyota Prius recall were sold in Europe and other markets. The company said that U.S. drivers can expect to start receiving recall notices through their mail sometime this month.

“If sufficient heat is generated, there is an increased risk of a vehicle fire,” a Toyota spokesman in Tokyo told CNN on Wednesday. He did not offer any more details on the matter as it is unclear whether or not the defects have caused any injuries, accidents or deaths.

TM stock fell close to 1% on Wednesday following the Toyota Prius recall.