(CNN) -- High levels of carbon monoxide in a Massachusetts church building Sunday sent at least 20 children to hospitals, a fire official said.
The incident occurred at St. Mary's Education Center in Waltham, deputy chief Michael Quinn of the Waltham Fire Department said.
The department got a call about a suspected gas leak while about 50 children between the ages of 8 and 12 were inside for Sunday school.
The children were evacuated and put in a church basement, Quinn said. When firefighters got to the scene, they determined the problem was spurred by elevated levels of carbon monoxide, not a gas leak.
Symptoms of exposure to elevated carbon monoxide levels include dizziness, headaches, and a pink hue to the skin, Quinn said.
Newton-Wellesley Hospital in Newton accepted 17 children who were transported, and Mount Auburn Hospital in Cambridge accepted three children. Seven parents took their children to their own physicians.