Four corrections officers were sent for medical evaluations after gas leak in an employee area of the Franklin County Jail over the weekend.
County employees are still investigating the cause of the leak that started Saturday afternoon in one of the power plant rooms, said Sheriff Jim Raymond.
Enough of the gas entered the locker room, break room and master control room to make four employees feel ill.
Two returned to work a short time later, and two were going to another checkup on Monday, he said.
No inmates were affected, Raymond said.