A "rust-colored material" expelled from ducts in a Wilmington DuPont lab prompted 18 workers to be evaluated at area hospitals, a spokesman for the company said Saturday.

The workers were contractors doing cleanup in a lab at the DuPont Experimental Station about 11 a.m. Saturday, spokesman Dan Turner said. They were wearing appropriate protective equipment, he said, but were evacuated after being exposed to the material released from ductwork. The incident brought area emergency responders to the facility, Turner said.

None of the workers showed signs of chemical exposure, Turner said, and all were released from medical treatment.

The material itself has not yet been identified, he said, but it was determined to be pH neutral and showed no sign of toxic hydrogen fluoride gas. The lab returned to normal operating conditions and there were no signs the surrounding community had been exposed to anything harmful.