Update 2:54 p.m. EST: Virgina Tech has lifted the lockdown, issuing this statement:

The campus alert is lifted. There will continue to be a large police presence on campus today.  Police have not received nor discovered additional information about a person possibly carrying a weapon beyond that reported this morning.  The university community may resume normal campus activity. Only Blacksburg campus classes have been cancelled today. 

Update 1:28 p.m. EST: In another alert on its website, Virginia Tech has cancelled classes for the rest of the day and asks that students and employees remain in doors:

Students are asked not to come to campus. The university understands that it has been several hours since this began.   Many officers from many police departments continue to search campus buildings. We have a very large campus and this will be a long process. There have been no further sightings or reports.

Update 12:57 p.m. EST: Police have released a composite sketch of the man who may have been holding a gun, according to three juveniles at the Virginia Tech summer camp. The University has posted the sketch on its website:

Update 12:07 p.m. EST: Virginia Tech has issued another alert on its website noting that police are continuing to search the campus and asking students to remain indoors. No one is in custody yet. CNN spoke with Lynn Davis, a spokeswoman for the university, saying officials are keeping the doors locked on campus.

Update 11:29 a.m. EST: Amanda Huchler, a student on campus on lockdown in Hahn Hall tells USA Today "The professor is still teaching. Everyone is calm and no one seems worried. Tech is doing a great job of keeping everyone safe and secure." Meanwhile, Larry Hincker, assistance vice president of university relations, tells the newspaper that the three students who said they saw the gunman were attending a camp called "Higher Achievement." He said "The alert is in effect until further notice. We are asking people to stay indoors until they hear from us again." Below

Update 11:05 a.m. EST: The alert is still in effect and police are still searching the campus, says a police official at an on-campus press conference. There is still no confirmation of a man holding a long-barreled gun with a short handle, reports MSNBC. The warning came from three youths attending a summer camp at the university, which was reported about two hours ago. The university is still under lockdown.

Students at Virginia Tech are under lockdown following a report that a man was spotted with what may have been a handgun. According to USA Today the police have not yet found anyone. NBC News reports that there's been no verification of the report, according to federal officials. At 9:37 a.m. the school issued an alert saying "three young people attending a camp at Virginia Tech reported seeing a man holding what may have been a handgun," the AP reports. "They said it was covered by a cloth or covering of some sort, and that the man was walking in the direction of the volleyball courts." A spokeswoman for the school tells CNN the "white male was described as having light brown hair and being 6 feet tall and was walking in the direction of a volleyball court. The man was wearing a blue and white striped shirt, gray shorts and brown sandals. He had no glasses or facial hair." The potential threat immediately summoned fears of the 2007 shooting at the Blacksburg, VA school where 32 people were dead and 25 injured.