Most General Motors Co. assembly plants will keep building vehicles during the automaker's traditional two-week summer shutdown next month, an unprecedented move to meet demand for certain vehicles, reported The Detroit News.

Nine of GM's 11 assembly plants, including four in Michigan, will keep producing from June 28 through July 9, and most of its U.S. stamping and powertrain plants also will remain operational, helping GM produce another 56,000 vehicles.

That would generate additional revenue for GM, which books sales when vehicles are delivered to dealers, not when consumers make purchases.

The production boost also would help alleviate a shortage of certain vehicles that has confounded GM this year, including the Buick LaCrosse sedan and the Chevrolet Traverse and GMC Acadia crossovers.

GM has added third shifts and overtime at several factories this year, but the automaker has struggled to boost record-low inventory levels amid a rebound in sales.

"When you look at the increase in production, and the reduction in its overhead cost structure, GM should make profits that look really good in the second quarter," said autos analyst Erich Merkle of Autoconomy.com in Grand Rapids.

The assembly plants that will stay open are: Detroit-Hamtramck; Flint; Lansing Delta Township; Lansing Grand River; Arlington, Texas; Bowling Green, Ky.; Fairfax, Kan.; Fort Wayne, Ind.; and Wentzville, Mo.

"We're rockin' and rollin,'" said UAW Local 602 President Brian Fredline, president of UAW Local 602. "We've barely been able to shut down the line for a day, so I'm not surprised."

Local 602 represents the GM Lansing/Delta Township plant where GM builds the Traverse, Acadia and Buick Enclave.

In April, the plant added a third, late-night shift and added 483 workers from GM's former Saturn plant in Spring Hill, Tenn. The Lansing/ Delta Township plant runs day and night Monday through Friday and some Saturdays. In total, the plant added 1,000 workers, Fredline said.