Operations returned to normal at a Willmar turkey-processing plant Saturday after 24 people fell ill late Friday and one was hospitalized overnight.
The cause of the illnesses remained unknown Saturday.
After officials could find no origin for the workers' flu-like symptoms, they closed the investigation at Jennie-O Turkey Store about 11 p.m. Friday, said Fire Chief Gary Hendrickson.
Rice Memorial Hospital workers initially had been alerted that 22 employees had symptoms of vomiting, coughing and shortness of breath. Seven ambulances and a bus were dispatched to the plant.
The 24 patients were treated in the hospital's emergency department by a team of physicians evaluating them for potential chemical exposure. The team consulted with the poison control center and the Minnesota Department of Health before releasing the patients.
Wendy Ulferts, chief nursing officer, said one woman was held overnight for observation. That patient had been released by Saturday afternoon, Ulferts said.
"We have conducted a thorough plant inspection with local fire officials and internal safety personnel, and found no cause for the event," company officials said earlier Saturday.
Employees had called first responders at 7:16 p.m. Friday on a report of a woman who was unresponsive at times at the plant at 1535 30th St. SW.
