General Motors has eliminated the third shift at its Spring Hill, Tenn., assembly plant due to the impact of the coronavirus pandemic, the company and UAW local said Wednesday.

“We believe the best way to react to this unforeseen change in our market is to reduce output and operate on two shifts effective immediately,” said GM spokesman David Barnas.

“This adjustment allows the plant to maintain stable production, protect the value of our brands in any sales environment, and to provide the smallest impact to plant employment going forward.”

About 680 full-time and temporary employees will be permanently laid off, Barnas said.

The layoffs won’t all come from the third shift, Mike Herron, shop chair for UAW Local 1853, which represents workers at Spring Hill, told Automotive News.

Employees with the highest seniority can move to either the first or second shift, while lower-level workers on those shifts may be laid off. The layoff process will be completed by July 31, Herron said.

“When we went down, there were three shifts of production, and demand was such that there were three shifts of demand,” Herron said. “The market just didn’t rebound quickly enough. We had hoped that it was going to be a complete rebound to our pre-coronavirus levels, and it just never materialized.”

The third shift, which has been laid off since GM closed plants in March to prevent the spread of the coronavirus, was scheduled to return to work June 21. Last week, GM delayed the return of the third shift indefinitely.

Some workers may be able to transfer to other GM plants, Herron said.

Spring Hill employs a total of 3,700 workers and builds the Cadillac XT5 and XT6 and the GMC Acadia.

“It’s heartbreaking to have to even make this announcement,” Herron said. “I can’t wait until the market rebounds in such a manner that everybody can come back to work because they certainly deserve it. They’re hardworking people.”

GM expects to reach pre-virus production patterns by the end of June.