It happened at about 2:30 p.m. Tuesday on the third floor of the Mendel Science Center in Mendel Hall.
Radnor Police tell Action News a freshman chemistry class was conducting an experiment when one of the students had a bad reaction. They thought she was having an asthma attack.
The student went into the bathroom, where she started to experience a nosebleed and nausea. Eight others, including the professor, started experiencing similar symptoms.
The fire alarm was pulled and the entire building evacuated.
"It was pretty scary actually," said freshman Ryan Wong. "I thought it was going to be a fire. I didn't expect this. Not good."
"Everyone just kind of left out of their classrooms and ran because we weren't sure what it was. We thought it was fire drill," said freshman Shakyra Greene.
About 230 firefighters responded to the scene. The student who experienced a nosebleed was rushed to Bryn Mawr Hospital, where she underwent decontamination before being let inside.
The others, whose symptoms were not as severe, underwent decontamination procedures on campus outside Mendel Hall.
"They're being triaged right now by the fire department," said Radnor Police Superintendent Bill Colarulo. "They're going through decontamination. They're going through showers. Once that's done they'll be taken to Bryn Mawr Hospital for treatment."
Police say firefighters have been able to identify the three chemicals that were being used in the experiment. Investigators say even though the chemicals were harmful, the injuries appear to be non-life-threatening.
The evacuation order for Mendel Hall remained in effect Tuesday night.
A section of Spring Mill Road in Villanova adjacent to the building was closed as the cleanup and decontamination work continued.
The university released the following statement Tuesday afternoon:
Villanova University evacuated Mendel Hall, an academic building located on its main campus, at approximately 2:30 p.m. this afternoon. This was due to a situation resulting from a laboratory experiment taking place on the building's third floor. Several individuals were transported to local hospitals for evaluation. Radnor Police, along with local fire and emergency responders are on the scene. The situation has been contained, but the building remains closed.