KITTERY, Maine (WGME) -- Investigators say they have determined the source of the carbon monoxide leak at a Kittery day care center that resulted in multiple children and adults being rushed to the hospital.

The fire marshal’s office said it operated the building’s heating system in coordination with Maine Fuel Board inspectors and found no concerns related to the emission of carbon monoxide.

The concrete saw was being used in a nearby suite that was under construction without a state building permit, and smoke detectors near the saw were covered up, authorities said.

Seven children were rushed to the hospital after a carbon monoxide emergency inside a Kittery, Maine day care.

The Maine Fire Marshal's Office said carbon monoxide that prompted the evacuation of a Kittery day care and led to nearly a dozen people being treated at an area hospital came from a gas-powered saw that was being used elsewhere in the building.