FILE- This Feb. 15, 2018, file photo shows a Ford logo on the grill of a 2018 Ford Explorer on display at the Pittsburgh Auto Show. Ford says it wants to reopen five North American assembly plants in April that were closed due to the threat of coronavirus. The three Detroit automakers suspended production at North American factories March 19, 2020, under pressure from the United Auto Workers union, which had concerns about members working closely at work stations and possibly spreading the virus. (AP Photo/Gene J. Puskar, File)

FILE- This Feb. 15, 2018, file photo shows a Ford logo on the grill of a 2018 Ford Explorer on display at the Pittsburgh Auto Show. Ford says it wants to reopen five North American assembly plants in April that were closed due to the threat of coronavirus. The three Detroit automakers suspended production at North American factories March 19, 2020, under pressure from the United Auto Workers union, which had concerns about members working closely at work stations and possibly spreading the virus. (AP Photo/Gene J. Puskar, File)

DETROIT (AP) — A tornado strike at a critical Ford manufacturing plant threatens to disrupt the automaker’s supply chain.

Ford disclosed in a regulatory filing Friday that the BorgWarner factory in Seneca, South Carolina, which makes a key transmission part for many of Ford’s most profitable vehicles, was severely damaged Monday when a twister rolled through.

Images reveal heavy damage throughout the area. Television news cameras showed the roof ripped off a large portion of the plant and severe damage inside.

Seneca produces transfer cases for F-Series pickup trucks, Ford Explorer and Expedition SUVs, Transit vans and the Lincoln Aviator and Navigator SUVs. Transfer cases shift power to a second drive shaft to run all-wheel-drive vehicles.

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Ford-owned equipment to make the parts was not “materially damaged” by the tornado, but neither Ford nor BorgWarner could say when production would be resumed. Ford closed all of its U.S. factories about a month ago due to the coronavirus outbreak.

The company is negotiating with the United Auto Workers union about reopening factories but hasn’t given a target date other than sometime in the second quarter. Rival Fiat Chrysler plans to reopen its plants on May 4.

F-Series pickups are the top-selling vehicles in the U.S. and are responsible for much of Ford’s profits. If the plant can’t come back online quickly, it could limit Ford’s production of the lucrative vehicles, further compounding virus-related financial problems for the Dearborn, Michigan, automaker. Earlier Friday, Ford disclosed that it expects to post a $2 billion first-quarter loss when it reports earnings April 28.

“We are working closely with the supplier to manage the situation and to determine next steps,” Ford said Friday.

BorgWarner is developing plans “as quickly as possible” to bring the factory back online, including contingency plans if it takes longer than it was expected to be closed due to COVID-19. “We are not giving guidance on a specific date,” spokeswoman Michelle Collins said in a prepared statement.

Ford said in a Friday bond-sale filing with the U.S. Securities and Exchange Commission that it doesn’t have enough information to predict when the BorgWarner factory will be back in operation “or whether or the extent to which this incident will impact our plans to resume production of four-wheel drive and all-wheel drive vehicles.”

BorgWarner wouldn’t say what other auto parts the plant manufactures or what companies they sold to.

Security guard Jack Harvill, 77, died when the building he was in outside the plant collapsed in the tornado. Only about five people were at the plant at the time. Typically, 200 would be working the night shift, but the coronavirus shut the plant down, Oconee County Coroner Karl Addis said.

Nine people were killed by tornadoes in South Carolina.