EXETER, N.H. (AP) — A hospital emergency department in New Hampshire is open again, one day after an unknown odor sickened 19 workers.

Nineteen staff members at Exeter Hospital were evaluated after some complained of dizziness and nausea on Friday morning. Officials say all had recovered by Friday evening.

The hospital shut down an inpatient operation room and the emergency room directly above it. Authorities said a thorough investigation by the state hazmat team and the National Guard was completed Friday night, but officials weren't able to determine the cause.

The emergency department reopened Saturday afternoon after extensive cleaning. The operating room is expected to reopen Monday morning.