The Lehigh Valley Academy Regional Charter School high school building on the 1600 block of Valley Center Parkway was evacuated "out of an abundance of caution," officials said on Facebook just before 2 p.m.
First responders and hazmat crews were on-scene Friday afternoon evaluating the affected students and staff, administrators added. They did not describe the symptoms experienced or characterize the illness.
At least 48 children and adults have been hospitalized following the incident, and police are asking residents to keep away from the building until further notice, according to the Allentown Morning Call.
Administrators said at about 2 p.m. that more information was forthcoming. As of Friday evening, the school had not issued an update on its website or social media channels.
This is a developing story.
Click here to follow Daily Voice Bethlehem and receive free news updates.