Employees at a Jennie-O Turkey Store processing plant in Willmar, Minnesota, were taken to a local hospital on Friday evening after a mystery illness caused about 30 workers to show symptoms such as vomiting and coughing.

Reports said that seven ambulances and a bus were dispatched to the scene and about two dozen employees were hospitalized. Most were treated and released, but one employee was admitted and was in a stable condition, according to Pat Solheid, Jennie-O Turkey Store vice president of human resources and administration.

That patient was released on Saturday afternoon, according to officials at Rice Memorial Hospital, quoted by the West Central Tribune.

Willmar's police, ambulance service and fire department responded to the incident after a call alerted them to a possible chemical leak at the plant.

After the drama of the medical situation, the company conducted "a thorough plant inspection with local fire officials and internal safety personnel and found no cause for the event," Solheid said.

According to USA Today, firefighters tested for carbon monoxide, carbon dioxide and ammonia and all three tests came back negative.

The facility has since reopened and returned to normal operations.

Jennie-O is owned by Hormel Foods Corporation. The company has processing plants in Willmar, Faribault, Montevideo and Pelican Rapids, Minnesota, and in Barron, Wisconsin.