Waltham, MA – Fire officials in Waltham say at least 20 people were taken to a hospital as a precaution because of a carbon monoxide leak at a local Sunday school.

Firefighters responded to St. Mary’s Religious Education Center on Sunday morning and detected high levels of carbon monoxide. Officials say there are no serious cases of carbon monoxide poisoning and everyone taken to Newton-Wellesley Hospital is expected to be OK.

Most of the people taken to the hospital were students ages 8 to 12.

Officials say they were called to the school after some adults began feeling dizzy and reported headaches.

The school’s heating system is shut down as investigators try to determine the cause of the leak. The school is expected to be closed for a few days during the investigation.