A Stony Brook University residence hall was evacuated when a chemical irritant was released into the air, causing students to vomit Sunday night.

Hand College, one of the university's dormitories located in Tabler Quad, was evacuated when a chemical was released on the third floor at about 7:10 p.m. Reports say some students felt nauseous, vomited or had eye and throat irritation.

Responding university police and fire marshals "became overcome by the irritants themselves," according to a statement released by Stony Brook University.

Students say the fire alarm sounded and after they evacuated, emergency responders kept them in quarantine for about three hours outside the building. About 100 students were kept in the area.

"A total of 20 students who were on or in the immediate vicinity of the third floor were decontaminated as a precaution. Of these students, a total of four were transported (treated and discharged) to University Medical Center with minor irritation complaints," says the university statement.

Unconfirmed reports say the chemical may have been tear gas but the university believes "it is likely that the substance was an irritant such as pepper spray or mace."

The residence hall was decomtaminated by Haz-Mat teams and reopened at about 10:30 p.m.

An investigation is ongoing.