Tests for carbon monoxide were negative, Mr Wilking said.
Residents and local fire departments were asked not to bring new patients to Exeter Hospital because of the evacuation.
Debra Vasapolli, director of Community Relations, said staff in the inpatient OR started experiencing for symptoms of dizziness, nausea and vomiting around 8:30 a.m. "In an abundance of caution. we evacuated the O.R".
If the gas builds up in an enclosed space, any people or animals in that space will be killed instantly.
20 patients are being treated on the scene.
Exeter Hospital is about 80 kilometres north of Boston
Vasapolli said the sick staff members were taken to the hospital's emergency room.
A statement from the hospital said all other hospital wings were unaffected by the problem and running as usual.
A New Hampshire hospital operating and emergency room were evacuated Friday due to a suspected chemical leak.
Their statement said most people affected by the problem are now feeling better. About 40 patients and some staff experienced flu-like symptoms after the odor was reported, the source of which remains a mystery, according to the Boston Globe.