General Motors closed its Pontiac Truck and Bus plant on Thursday, sending 2,500 workers home. On Friday, it announced it would suspend work at pickup and SUV plants in Flint, Mich., and Ft. Wayne Ind., and another plant in Oshawa, Ontario.

The plants would all close at the end of Friday's second shift, company spokesman Tom Wickham said.

The plants assemble full-size Chevrolet Silverados and GMC Sierras, The Detroit News reported.

The company has said it has an up to four-month backlog of trucks to sell, but not enough parts to keep production going. Detroit-based American Axle & Holding produces suspension parts, but closed its plants Tuesday when 3,600 workers at five factories walked off the job demanding higher wages.