Multiple children at a Pennsylvania day care were sickened Tuesday morning after carbon monoxide leaked in the building, officials said.

Fire trucks and ambulances responded to Happy Smiles Learning Center in Allentown just before 7 a.m.

Lehigh Valley Hospital - Cedar Crest is treating 14 children and one adult, all of whom were in stable condition, a Lehigh County Hospitals spokesman told Fox News Digital. An additional four children were rushed to Lehigh Valley Hospital 17th Street, the spokesman said. Their conditions were not immediately known.

According to WFMZ-TV, 28 children and four adults were rushed to four nearby hospitals, where they all were in stable condition.

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All of Allentown’s ambulances were responding to the leak, according to the station. Multiple children were reportedly carried out of the day care on stretchers and taken to hospitals across the Lehigh Valley.

first responders outside daycare

Multiple children were sickened after carbon monoxide leaked in a day care in Allentown, Pennsylvania. (FOX29 Philadelphia WTFX)

As some children remained at the scene awaiting transportation, a neighboring day care was allowing the children to stay there and keep warm, the report said. 

ambulance and fire trucks outside daycare

All the ambulances in Allentown, Pennsylvania, reportedly responded to the incident. (FOX29 Philadelphia WTFX)

Officials said that parents have been notified of the incident. 

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The emergency call was prompted when one child fell unconscious. Responding firefighters detected carbon monoxide and initiated a full evacuation.

Officials told the station that the building had no carbon monoxide detector.

Fox News' Paul Mitchell Picasso and Haley Chi-Sing contributed to this report.