TUCSON, Ariz. (AP) — Police searched a building on the University of Arizona campus Friday night after receiving a report of a gunman, but no sign of a shooter was found.

The campus police department told The Associated Press that officers gave the all-clear and the area of the campus was reopened Friday night.

A few hours after the search began, the department's Twitter site said: "UAPD has cleared the Admin Bldg. No one was found, no injuries or signs of a shooting. The Stu Union IS OPEN."

Campus police spokesman Sgt. Juan Alvarez said earlier that police received a 911 call about a man with a rifle at the Administration Building, and numerous officers responded. A text alert was sent to students and staff about the situation, instructing them to stay away from the area.

The Administration Building and some surrounding buildings near the campus's central mall were evacuated. Streets leading to the Administration Building were blocked, and dozens of police officers — some wearing helmets and armored vests and others armed with assault weapons — were seen on campus with a helicopter hovering overhead.

Alvarez said police did a floor-by-floor search.

A shooting at the University of Arizona's nursing school in October 2002 left three professors dead before the gunman killed himself.