Nio, Chinese electric vehicle (EV) maker often pegged as a challenger of Tesla in China, is launching a mass recall of its flagship ES8 car model due to safety concerns related to its battery packs.

The recall, effective today, affects 4,803 Nio ES8 vehicles whose battery packs contain NEV-P50 modules which were manufactured between April 2 and October 19 last year. The recall plan covers more than a quarter of all ES8 units solds. As of the end of May, Nio had delivered 17,550 ES8.

The defected NEV-P50 modules, in the most extreme cases, could lead to overheating and spontaneous combustion of the battery pack, according to China’s State Administration for Market Regulation.

Nio would provide free replacement battery packs for all affected vehicles.

The Shanghai-based company confirmed on its Sina Weibo earlier this month that an ES8 caught fire in a parking lot in the city of Wuhan–the third spontaneous combustion incident in just two months.

Last Monday, the Ministry of Industry and Information Technology issued a notice asking EV makers to promptly report any vehicle-related fire incidents to the authority.