Advertisement - Continue Reading Below

About 20 children attending Sunday school in Waltham were taken to the hospital Sunday morning after a carbon monoxide leak made several students and teachers sick, Waltham authorities said.

Fire officials said they measured “extremely high” levels of carbon monoxide in St. Mary’s Religious Education Center on Pond Street. Teachers at the Sunday school called for help around 9 a.m. after several instructors and students felt dizzy and light-headed, said Deputy Chief Michael Quinn, of the Waltham Fire Department.

The children, who ranged from 8 to 12 years old, were taken to Newton-Wellesley Hospital with non-life threatening injuries, Quinn said.

“To the best of my knowledge, they’ll all be released soon,” he said Sunday afternoon. “A lot of it was precautionary.”

There was a total of about 50 children and a handful of staff in the building at the time of the leak, Quinn said. Every one was evacuated, and a few instructors were also evaluated, he said.

The building’s heating system was shut off and contractors have been investigating how the leak happened. No one can use the building until the problem is solved, Quinn said.

“I know they were going to check the boilers, the chimney and the hot water heater,” he said. “Those were the only 3 appliances running in the building.”

Quinn said officials were still trying to determine if the religious school had carbon monoxide alarms.

Carbon monoxide, a colorless and odorless gas found in combustion fumes, can cause dizziness, weakness, and nausea. High levels of the noxious gas can be lethal, according to the US Centers for Disease Control.

Quinn said residents should install carbon monoxide detectors in their homes and businesses to prevent poisoning from the gas.