Marysville, OH — Seven people were hospitalized in critical condition Saturday after suffering from carbon monoxide poisoning at a Hampton Inn in Ohio, officials said.

A total of nine people were taken to local hospitals, according to The Columbus Dispatch. Marysville Fire Chief Jay Riley told the newspaper that the source of the carbon monoxide was unclear but everyone who was hospitalized had been in the hotel’s pool area.

Riley said the victims included both children and adults. He did not provide exact ages.

The hotel was evacuated shortly after. Brooks told the newspaper that all of the injured were alive when they were transported and that seven of the patients were in critical condition.

Two others were treated at the scene, and five more later sought treatment on their own at a hospital, Brooks said.

The Dispatch could not reach any members of the hotel management late Saturday. Riley said a Hampton Inn maintenance team was en route from out of state.

Marysville is about 30 miles (48 kilometers) northwest of Columbus.