General Motors Co said on Friday it is issuing a new recall for nearly 69,000 Chevrolet Bolt electric vehicles (EVs) worldwide for fire risks after reports of two fires and will replace defective battery modules as needed.

The Bolt EVs were recalled in November for fire risks and at least one of the two new fires was in a vehicle that had already had the software update released as part of that recall.

The latest recall comes after GM and National Highway Traffic Safety Administration (NHTSA) regulators last week urged Bolt owners to park their vehicles outside and away from homes after charging.

The largest US automaker said “experts from GM and (battery maker) LG have identified the simultaneous presence of two rare manufacturing defects in the same battery cell as the root cause of battery fires in certain Chevrolet Bolt EVs.” GM said it will replace defective battery modules in the recall population, although it is not clear how many are defective.

The recall includes 50,925 US vehicles.

GM and LG engineers are working “to finalize all the steps of the recall repair process.

That would include a potential dealer inspection process,” GM said, adding that it “could replace full packs or suspect modules.”

“The question is whether GM has the technological capability to detect and identify defective batteries. If there is not, they may have to replace the total batteries, which will be costly, like Hyundai did,” said South Korean battery expert and professor Park Chul-wan.