(NEXSTAR) – Dozens of people have been taken to the hospital after a carbon monoxide leak at a daycare center in Pennsylvania, according to local authorities.

First responders were alerted to the incident shortly before 7 a.m. following reports of an unconscious child at the Happy Learning Smiles Center in Allentown, Lehigh Valley Live reported.

A total of 27 people were transported to various hospitals in the area, WPHL reported, citing first responders at the scene. Fire officials tell WPHL there were 25 children and 8 workers inside the building at the time of the incident.

A representative for the Allentown Police Department directed questions to local fire officials but confirmed officers were on-site to secure the scene. A spokesperson for the Allentown Fire Department did not immediately respond to Nexstar’s request for further information.

Capt. John Christopher of the Allentown Fire Department told WFMZ that every ambulance in the city had responded to the day care center Tuesday morning. The outlet added that officials were calling the incident a “level 1 mass casualty” incident, meaning hospitals in the area should prepare to be overwhelmed.

All of the sickened individuals were said to be in stable condition, reports indicate.

This is a developing story. Check back for updates.