A hospital in New Hampshire reportedly had a “chemical release” in its emergency room that affected multiple patients on Friday.

At least 20 patients from the Exeter Hospital were evacuated from the emergency room to an area outside the hospital for treatment, according to NBC Boston. At least 17 hospital staff members were also evacuated from the building, according to CBS News. Aerial footage from local media outlets captured patients on hospital beds outdoors and doctors treating them.

The hospital told CBS News in a statement that a few patients reported dizziness Friday morning from “an unknown cause.” The hospital shuttered the operating and emergency rooms “out of an abundance of caution.”

Epping Fire told NBC News they were called for a “carbon monoxide problem.”

"What we know is patients were being treated in the [operating room] with flu-like symptoms when those treating them also started feeling ill, so the OR was shut down and people were moved to the ER for treatment," the town manager, Russell Dean, said following the incident.

"The same thing happened there, so the ER was shut down and a staging area has been set up outside the main hospital, with patients being transported to area hospitals."

Dean said officials are investigating what caused the possible leak.