MADISON, Neb. – An anhydrous ammonia leak at the Tyson Fresh Meats pork plant in Madison, Neb., caused at least 40 workers to be taken to local hospitals, according to news reports.

All the workers were exposed to ammonia, according to a spokeswoman for Faith Regional Health Services in Norfolk, Neb. Local news reports said 10 people were transported by ambulance. They were assessed for the severity of inhalation and potential contamination, according to a hospital spokeswoman.

“We're investigating the cause of an ammonia leak that happened at our Madison pork processing plant Thursday evening just before 8 pm, said Gary Mickelson, Tyson spokesman. “The plant was not in full production at the time, however, there were about 150 people present, and most of them were working in our second shift ham boning operation.

Mickelson said the plant was evacuated and, as a precaution, 40 workers were taken to local hospitals for evaluation. They have all been released, he said.

“Tyson maintenance workers repaired the ammonia line involved in the leak,” he added. “Ammonia is used as a part of the plant’s refrigeration system.”

Tyson employs 1,100 workers at the plant, which was not damaged and is currently in operation. The plant is the largest employer in Madison, which has a population of about 2,438.