Updated

A Villanova University classroom building is reopening after an accident that sickened members of a freshman chemistry class.

Officials at the private Catholic school in suburban Philadelphia say it happened around 2:30 p.m. Tuesday at the Mendel Science Center and the building had to be evacuated. Police, fire and other emergency officials responded.

Police in Radnor say about 30 people were treated and decontaminated after the accident. School officials say the building is reopening for classes Wednesday.

Officials haven't said what led to the accident. Police say most of the injured were having trouble breathing, and some suffered nose bleeds. Several others experienced more severe symptoms.

During the incident, students on campus say they received an alert to stay away from the science center.