All of the people were treated and released, the company said in a news release.
Roads around the plant, including Interstate 90, were briefly closed, and people working around the plant were ordered to stay indoors and close doors and windows, the Grant County sheriff's office said.
"We regret this incident and its impacts on the community," said Jeff Johnson, director of operations for the REC plant.
Warning alarms at the plant went off at 7:05 a.m., and a chemical cloud appeared shortly after that, drifting to the south. The cloud contained silicon tetrachloride and trichlorosilane, which can react with moisture to become an irritant to membranes in the nose and throat, the company said.
No ground-level concentrations of the chemicals were detected, however, and the cloud dissipated, the company said. Plant managers sounded the all-clear siren before 10:30 a.m.
The company said it will investigate to determine why the chemicals were released.
REC makes silicon components for the solar energy and electronics industries.
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