Ford said Friday its battery supplier, SK, has started building battery cells again at a plant in Georgia but it will take time “to ensure they are back to building high-quality cells and to deliver them to the Lightning production line.”

“The teams worked quickly to identify the root cause of the issue,” Ford said in a statement Friday. “We agree with SK’s recommended changes in their equipment and processes for SK’s cell production lines.”

Ford last week said it expected Lightning production to be down through at least this week, as engineers determined the root cause of the battery issue and implemented improvements to the manufacturing process.

The fire occurred Feb. 4 in a holding lot during a pre-delivery quality check while the vehicle was charging, followed by Ford suspending production and issuing a stop-shipment of the vehicles to dealers. Ford said engineers determined there was no evidence of a charging fault.

Ford said it is not aware of any incidents of this issue in vehicles that have already been delivered to customers and dealers.

The F-150 Lightning is being watched closely by investors, as it’s the first mainstream electric pickup truck on the market and a major launch for Ford.

The battery issue adds to ongoing “execution issues” detailed to investors earlier this month by Ford CEO Jim Farley that crippled the automaker’s fourth-quarter earnings.