Tweets from Exeter Professional Firefighters say crews were dispatched to Exeter Hospital for an odor investigation in the emergency room.
Video from SkyEye shows a large number of people seated on stretchers in the grass outside the hospital.
An estimated 12 staff were transported to other hospitals while others were treated and released, Exeter Assistant Fire Chief Eric Wilking told the Union Leader newspaper.
Multiple Staff Members Treated Following'Chemical Release
A statement from the hospital said all other hospital wings were unaffected by the problem and running as usual. 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.
Exeter fire officials said they initially received a call for 20 ambulances, but not all of them were ultimately needed. At this time, the cause is unknown. The latter was closed out of "an abundance of caution", she said.
Exeter Police are recommending that residents seek alternate emergency facilities for treatment.