Image copyright Facebook Image caption An estimated 12 staff were transported to other hospitals

A hospital in the US state of New Hampshire has been evacuated after operating room staff complained of nausea due to an "unknown odour".

Exeter Hospital cleared its emergency room on Friday morning out of an abundance of caution, spokeswoman Debra Vasapolli told local media.

About 17 members of staff were affected by the incident, including some who experienced dizziness, she added.

Fire and police officials were at the scene investigating the incident.

The operating and emergency rooms were closed during the evacuation, Ms Vasapolli said.

The incident began at about 09:00 (13:00 GMT) when four employees began complaining of headaches, dizziness and nausea, according to Dr Neil Meehan, the hospital's chief physician assistant.

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.

"There are a number of issues. It could be outside air coming in as a contaminant. We're looking at cleaning fluids that could have been used in the hospital," he told the newspaper.

Tests for carbon monoxide were negative, Mr Wilking said.

No patients experienced any symptoms but six were transported from the emergency room, she added.

Fire department officials said they have found no liquid spills, leaks nor gas in the operating room, local media reported.

The emergency department and inpatient operation rooms remained closed, but other areas of the hospital were re-opened, according to Ms Vasapolli.