A person with a gun was reported on Virgina Tech’s campus Thursday morning, according to school officials, but so far, authorities have not been able to find a gunman.

The campus was on alert for almost six hours, but the alert was lifted at about 2:40 p.m. Before then, Virginia Tech was on a lockdown, and by mid-day, officials had canceled all summer school classes for the day, and asked that people stay away from campus. The university’s football team delayed its first practice until later this afternoon.

Despite the caution and a massive search for the purported gunman, police had not found him. The report came from three 14-year-olds attending an academic camp at the Blacksburg campus. Police said no other witnesses have come forward saying they had seen a gunman.

“At this point no one has been able to confirm whether or not there was an actual gun on campus,” said Blacksburg Police Department spokesman Lt. Steve Taylor.

Several people have been questioned, but nobody was in custody, campus police Chief Wendell Flinchum said during a press conference on campus.

A number of public safety agencies, including State Police and officers from nearby police departments, have been searching the campus, the university said.

From the university's web site.

“Person with a gun reported near Dietrick,” an alert posted at 9:37 a.m read. “Stay Inside. Secure doors. Emergency personnel responding. Call 911 for help.”

The University also asked anyone with information to call campus police tip line at (540) 231-6411.

Dietrick Hall is described as a “dining center” that also has a convenience store, bake shop and laundry facility, according to the university’s web site.

In another item posted at 10:08, the university’s web site reported that:

Composite sketch of reported gunman at Virginia Tech (Virginia Tech University)

Flinchum said police so far have not found anyone matching that description.

Police further questioned the three campers and deemed their information credible, Flinchum said, which triggered the initial campus alert at 9:09.

Flinchum emphasized that the report police received said the suspect was carrying a handgun, “not that they pointed the weapon or threatened anybody.”

The teenagers were attending a camp sponsored by Higher Achievement, a District-based academic organization serving middle school students from underserved areas.

“Higher Achievement can confirm that our scholars were on campus during the situation at Virginia Tech,” Richard Tagle, CEO of Higher Achievement, said in s atatement. “Our organization was visiting the university as part of our summer academic program for middle-school youth in Washington, DC. Our first priority is the safety of our scholars and staff. We have been in contact with them and we have received confirmation that everyone is safe, and are proactively reaching out to parents of students who were on campus.”

Sensitivity to campus safety and security issues has been heightened on the Blacksburg campus since a gunman killed 32 people and himself in April 2007.

Larry Hincker, a university spokesman, said perhaps several thousand students were on campus Thursday morning for summer school, fall sports and summer camps.

"We really need to communicate first and investigate later, and that’s what we did," Hincker said.

The morning news conference was held on the steps of Burress Hall in the middle of campus, and though the school’s alert asked everyone near Virginia Tech to remain inside, there were several people walking around the school’s drillfield. There was also a normal amount of car traffic in Blacksburg’s downtown area just off campus.

Virginia Tech revamped its alert system following the 2007 shootings. A university official said Thursday more than 48,000 students and campus personnel received a text message alert about the situation, and an email alert was sent out to every student and school employee.

Hincker said the school is “proceeding with an abundance of caution” and that people walking around campus were doing so “on their own volition.”

"We’re in a new era,” he said. “Obviously the campus went through something terrible four years ago and the choice facing us and particularly the police departments is when you get a report, what are you going to do with the report, regardless of what the veracity may be or the ultimate conclusion might be. In our particular case, and I believe what most campuses would do, is regardless of what your intuition and experience as a public safety officer tells you, you really are forced to issue an alert. That’s where we are right now.”

Alex Watt, 19, a sophomore from Springfield, said she and fellow students got text alerts from Va. Tech about the lockdown around 9:45 a.m. She had arrived early for a class and the building she was in – Burchard Hall – was immediately closed. She was kept in her classroom for about an hour, but then was allowed to roam around the hall. She and other students texted and called back-and-forth to get the latest information on the situation.

 She said the alert was unsettling, but said the she felt the building she was in was secure.

 “We’re in Blacksburg and because of the history, it makes it scarier,” Watt said.

Post staffers Mike E. Ruane, Justin Jouvenal and David Marino-Nachison contributed to this report.

This item has been updated.