NEW YORK (Reuters) - Nineteen staff members were evacuated from a hospital in Exeter, New Hampshire, on Friday and treated for dizziness, nausea and vomiting, a hospital spokeswoman said.

By mid-afternoon, officials at Exeter Hospital had yet to determine what caused the incident, which began between 8:30 a.m. and 9 a.m. EDT when five staff members complained of feeling dizzy, spokeswoman Debra Vasapolli said.

Other staff members in the hospital’s operating room later became ill, she said. The hospital initially said patients were among those affected, but Vasapolli said it was only staff members.

“No source has been determined at this point,” Vasapolli said. “In an abundance of caution ... we evacuated the O.R. (operating room) and closed it, as well as the emergency department, until we can determine the source.”

The affected staff were being treated in the parking lot and on grassy areas outside the hospital, which is about 50 miles north of Boston. Twelve of those who felt ill were sent to other facilities and seven were released, Vasapolli said.

The fire department in neighboring Kingston said it sent two ambulances to the scene.