HELENA - The Ash Grove Cement Co. plans to suspend production at nine of its 10 plants in the United States, some starting as soon as mid-November.

The company announced Thursday that "adverse economic conditions" led to the decision, which includes idling the Montana City plant. Fifty of the plant's 79 employees will be let go, beginning around Nov. 30.

Plant manager Dick Johnson says sales have been off quite a bit and the plant has full inventory. He says it's likely production will resume in the spring, when demand for th eproduct resumes for the summer construction season.

Johnson says the remaining staff of 29 will handle sales, maintenance and upkeep of the plant in anticipation of a return to full operations.

Ash Grove is based in Overland Park, Kan.