Oct. 11 (UPI) -- A carbon monoxide leak at a daycare in Allentown, Pa., sent more than two dozen children and several workers to the hospital Tuesday.
WFMZ reported that every ambulance in Allentown responded to the leak at the Happy Smiles Learning Center.
According to Capt. John Christopher, the original 911 call was for an unconscious child. When firefighters and EMTs responded, the monitors on their bags alerted them to carbon monoxide.
All of the 28 kids and four adults that were taken to the hospital are in stable condition.
The incident was reported as a level 1 mass casualty incident, meaning local emergency responders and hospitals may be overwhelmed by the number of patients.
UGI Utilities, a gas and electric company arrived at the daycare center around 8 a.m., according to spokesperson Joseph Swopes. Swopes told USA Today that the incident was caused by "a malfunctioning heating unit, as well as a blocked venting system."
"We have multiple people on site doing precautionary checks of the area," he said, adding people were evacuated due to safety concerns.
There is no carbon monoxide detector in the building, officials said. Legislation passed last month now requires all childcare centers in Pennsylvania to have CO detectors, but the 30-day deadline is not yet up.
