Two more Hanford Nuclear Reservation workers have reported feeling ill after exposure to some chemical vapors.
The incident occurred Monday at the former plutonium production site in south-central Washington.
The workers were checked out by medical personnel and cleared to return to work.
Contractor Washington River Protection Solutions says the workers were working at a laundry trailer outside the SY tank farm and were taken to the onsite medical provider for evaluation.
Hanford technicians are looking for the source of the vapors.
There have been several incidents at Hanford this year in which workers have reported feeling sick after exposure to chemical vapors.