Twelve workers at a Valley deli plant are recovering Monday night after being exposed to high levels of carbon monoxide. Now authorities are trying to pinpoint the cause. It happened Monday morning in Mount Jackson. It all started when an employee passed out this morning at One Stop Deli in Mount Jackson, when rescue crews got to the plant, they found they had more than just one patient to treat.

Gina Eaton, production manager at One Stop Deli in Mount Jackson says Monday morning an employee came and got her to let her know one of their workers had passed out. "So I went in and she was laying on the floor, she had passed out and after that we had found that just about everybody in there either had a headache or was dizzy this morning," says Production Manager Gina Eaton.

All 12 people were in the same area, the production room. When Eaton got into the room, she started to feel some of the same symptoms. "When I got in there, I felt like my chest was heavy, like it was hard to breath and the maintenance guy who had been outside all morning also said that when he was in there, just for the little bit of time that he was in there, that he was starting to get a headache," says Eaton.

Fire officials found high levels of carbon monoxide inside the building, and Shenandoah Memorial Hospital confirmed through testing that the employees had carbon monoxide levels in their blood. "It can be very serious, levels that high, and people exposed to levels that high and for a long period of time, respiratory distress can get very serious, you can become unconscious, and it can be fatal," says Gary Yew, Shenandoah County Fire and Rescue Chief. Fatal, which is why Chief Yew recommends for manufacturing facilities to have carbon monoxide detectors.

Chief Yew says the 12 patients at the hospital are in good condition. As for the building, it has been aired out and it's safe for people to return back to work. Authorities believe the source of the carbon monoxide is a commercial dryer that runs off of gas.