State epidemiologists are investigating an apparent outbreak of food poisoning that led to an evacuation at a FedEx sorting facility in Anchorage last week.

"Staff will be sending clinical and food samples to a reference laboratory for testing today," Susan Morgan, a spokeswoman for the Alaska Department of Health and Social Services, said Wednesday.

Four employees became sick in a Dec. 20 incident that caused the employee evacuation of the large processing warehouse near the airport, according to FedEx spokesman Chris Stanley.

Three of them were taken to the hospital, where they were treated and released, he said.

Firefighters trained to deal with hazardous materials swept the 500,000-square-foot building with sensors, but found nothing.

The employees were later diagnosed with food poisoning, he said. Stanley could not say what the employees ate that caused the illness or whether it was eaten at work.

Epidemiologists are now contacting the people who were involved in the "illness cluster," Morgan said. She had no information about the food the caused the illness.