Twenty-eight employees at a Willmar turkey-processing plant fell sick on Friday evening, and 21 of them were treated at a hospital.

Fire officials could find no origin for the workers' flu-like symptoms and closed the investigation about 11 p.m., said Willmar Fire Chief Gary Hendrickson.

Police and firefighters had brought in extra ambulances and a bus to transport workers from the evacuated Jennie-O plant to Rice Memorial Hospital in Willmar. One was admitted, company officials said early Saturday, and the plant was again up and running.

Hendrickson said there were no readings of any type of noxious gases or fumes in the plant, including carbon monoxide. "Everything was normal operations, as it would be on any other day," he said.

Additional medical personnel were called in to treat patients from the plant, a hospital employee said.

Employees had called first responders at 7:16 p.m. on a report of a woman who was unresponsive at times at the plant at 1535 30th St. SW., Hendrickson said.

Within moments came another call of a second employee vomiting in a bathroom, and soon more were becoming ill with vomiting and coughing.

Some patients were in kind of "an excited delirium," according to police scanner transmissions.

Jennie-O, owned by Hormel Foods of Austin, Minn., released this statement Friday night: "We are working with local authorities and investigating the matter thoroughly. The fire department is conducting a review of the plant and at this time, has not found anything unusual.

"The health and well-being of our employees is our top concern during this time. Our employees are being evaluated by local health care professionals this evening."