At least 10 people were injured, eight critically, after a chlorine leak at Pacific Steel and Recycling in Spokane, authorities said.
Most of those transported to area hospitals had respiratory issues, according to the Spokane Police Department.
Employees at the recycling center were working with a steel barrel when it was punctured and a "yellow vapor" started coming out. Authorities said those immediately around the barrel were affected, and then the wind carried it outside.