ALFRED -- Students, faculty and staff on an upstate New York college campus were directed to stay inside and classes were canceled Tuesday while police investigated a report of a young man possibly carrying a gun.

Police were conducting a door-to-door, building-by-building search on the campus of Alfred University in the state's Southern Tier. Classes were canceled and libraries were closed late Tuesday afternoon as the search continued.

Alfred's 232-acre campus is about 80 miles south of Rochester in Allegany County.

An alert on the school's Web site at 3:33 p.m. said police were investigating a report of a man, possibly carrying a gun, who was wearing a green hooded sweat shirt and carrying a backpack. A 4:04 p.m. update said the search was continuing.

The alert advised students, faculty and staff against going outside until further notice.

Town of Alfred police, Allegany County sheriff's deputies and state troopers were on campus, along with campus officers, Alfred spokeswoman Debbie Clark said.

"They're going through most of the classroom buildings now," she said. Three buildings had been cleared and closed as of 5:30 p.m.

About 2,000 undergraduate and 300 graduate students attend Alfred.