In separate incidents earlier this year, MMC reported a fire in a i-MiEV battery pack at the Mizushima battery pack assembly plant; and heating and melting in a pack installed in an Outlander plug-in hybrid electric vehicle.

Mitsubishi Motors’ investigation found that batteries that had been improperly dropped as part of the screening process were included in supplies from Lithium Energy Japan.

The automaker stopped assembling other models that use the same batteries, including its i-MiEV electric car, and recalled a total of roughly 1.2 million vehicles in June. It said that production of these models had already resumed by early this month.

The Nikkei said that MMC will now produce 2,000 Outlander PHEVs a month, and will double output by next May by taking such steps as consolidating the installation processes for batteries and motors.

Mitsubishi Motors currently has back orders for roughly 18,000 of the plug-in Outlanders worldwide. Because of limited battery availability, it will postpone shipments to the US for the time being and focus on filling orders in Japan, Europe and elsewhere, the report said.