escalated its strike against the Big Three automakers on Monday – specifically against Stellantis this time. Workers at Stellantis’ Assembly Plant in Michigan — approximately 6,800 of them — walked off the job, according to .

The factory is the only builder of – an incredibly profitable and important vehicle for the automaker, reports. The sudden move is the first expansion of strike since October 11 that builds Super Duty pickups, the Ford Expedition and Lincoln Navigator. Now, over 40,000 UAW workers are on strike.

The UAW made the announcement in a statement on its website:

“The move comes just days after UAW President Shawn Fain detailed the current proposals across the automakers, highlighting the shortcomings of Stellantis’ current offer.

Despite having the highest revenue, the highest profits (North American and global), the highest profit margins, and the most cash in reserve, Stellantis lags behind both Ford and General Motors in addressing the demands of their UAW workforce. Currently, Stellantis has the worst proposal on the table regarding wage progression, temporary worker pay and conversion to full-time, cost-of-living adjustments (COLA), and more.”

, Fain said the UAW and have “had talks through the weekend,” but he felt “like it was time to turn it up.”

“They know where we need to be. We can get there. We can get a deal done this week,” Fain told the outlet. “But the company’s got to get serious and get down to business.”

The strike against the Big Three first started back on September 15, and it has since expanded to cover 10s of thousands of auto workers around the U.S.