Watch video of police lockdown of central campus:

Hear Fernanda Echavarri's wrapup story:

A call to 911 Friday reporting "a man with a rifle" and a shooting in the University of Arizona Administration Building prompted a shutdown of much of the central campus and a search of the building. Police found no one with a gun and no sign of a shooting.

The center of campus was on lockdown, several buildings were evacuated, and no one was allowed into the area from shortly after the time of the call, 4:52 p.m., until about 9:15 p.m.

“An initial call came into the 911 system from a third-party operator to the University of Arizona Police Department at 4:52 p.m., indicating there was a male with a gun strapped to his chest and carrying a rifle,” UA Police Officer Joe Bermudez said. “The caller also said a shooting in the Administration Building had occurred and asked where the police were.”

Bermudez said the seven-story Administration Building was searched "floor by floor, room by room," a process that took three hours.

Dozens of police officers with rifles and other guns drawn swarmed the center of campus. Many were seen entering the Administration Building between 5 p.m. and 6 p.m. Bermudez said SWAT teams, police K9s and two bomb squads were on the scene.

“No shots were heard and no unusual activity was seen,” Bermudez said. “During the search of the building, no one was found, nor were there signs that a shooting had taken place in the building.”

Hear the UA Police Department official statement about the incident, read by Bermudez:

PHOTO: Mark Duggan, AZPM

The first text message alert to the campus was sent at 5:06 p.m., followed by Twitter messages starting at 5:15 p.m.

The Administration Building was ordered evacuated a short time later, followed by police telling occupants of a building to the east, Modern Languages, to evacuate through the east doors. The Student Union building to the west of Administration also was closed down.

"There's a report of a man with a rifle in the Administration Bldg," a UA Twitter alert said at 5:15 p.m. "UAPD is on the scene. Please stay away from the area."

The university issued eight alerts through its emergency email and text message alert system during the search.

No one among the evacuees of the building who were interviewed reported seeing a man with a gun or any other unusual activity inside except for the police presence.

State Rep. Ethan Orr, R-Tucson, was inside the Administration Building meeting with a UA official when the official got the campus alert on his mobile phone.

Orr said they were told "just shut the office and wait." He said he and the official waited about an hour before being told to evacuate.

AZPM's Christopher Conover speaking to state Rep. Ethan Orr:

The Administration Building is in the heart of the campus on the north side of the UA Mall along University Boulevard and just east of the Student Union building.

Much of the campus was closed during the search. Police allowed motorists parked in a garage to the north of the Administration Building to depart in their vehicles.

In October 2002, a UA nursing student who was failing his classes shot and killed three professors in the College of Nursing Building before killing himself in a classroom.

PHOTO: Christopher Conover, AZPM

AZPM reporters Christopher Conover, Mark Duggan, Andrea Kelly and Fernanda Echavarri and videographer Martin Rubio contributed to this story.