A New Hampshire hospital's emergency department has been evacuated because an unknown odor was detected.

Ambulances responded to Exeter Hospital on Friday to evaluate more than 20 people, some of whom complained of dizziness. Patients were seen on stretchers outside the hospital.

Calls for assistance were made at about 11:15 am. Operating and emergency rooms were evacuated.

The cause of the odor is being investigated. Messages left for a hospital spokeswoman haven't been returned.