ALLENTOWN, PA (WPHL)- An early morning carbon monoxide leak at an Allentown daycare facility sent 27 people to nearby hospitals on Tuesday morning, according to first repsonders.

Officials say they initially got a call for an unconscious child inside the Happy Smiles Learning Center along the 400 block of West Wabash Street. Upon arriving, officials say first responders’ carbon monoxide detectors on their equipment started going off. That’s when officials upgraded the call to a mass casuality incident.

According to investigators, 27 people in total were transported to four area hospitals. Officials say children and workers were among those who sought medical treatment. Fire officials tell PHL17 there were 25 children and 8 workers inside the building at the time of the incident.

According to the fire department, all of those who went to the hospital are now in stable condition.

It’s not yet clear what the source of the carbon monoxide leak was.

Stay with PHL17 for updates on this developing story.