UPDATE: Lauralton Hall students were sent home early Tuesday after being exposed to pepper spray.

At about 10:15 a.m., Milford Fire dispatch received a 911 call reporting the release of an unknown substance inside of the school lobby. About 30 to 40 students were initially exposed due to their close proximity during a change of classes, said Fire Battalion Chief Anthony Fabrizi.

"Many of the students began to experience respiratory irritation and difficulty breathing," Fabrizi said. "Students and staff evacuated the building, relocating to the school’s gymnasium."

Firefighter/EMT and paramedic units were dispatched to the scene.

Students and staff were evaluated and triaged by fire department personnel. Many students were treated on the scene by fire department paramedics and EMT’s. Many of the students were required to shower and change clothing in order to minimize their exposure, officials said.

"Ten students were transported to local hospitals including Milford, Yale, and St. Vincent’s for evaluation. None of the symptoms were life threatening," Fabrizi said.

The affected building was ventilated and metered as a precaution by fire personnel, and determined safe to re-enter.

Milford police were on the scene to investigate, and determined that the product released was in fact pepper spray. The motive and the person responsible are under investigation. Students and faculty were allowed back into the building, and an early dismissal was planned, Fabrizi said.