Virginia Tech officials lifted an alert issued after three people reported seeing a person possibly carrying a gun on campus.

The school says a large police presence will remain as officers continue to check out campus buildings, but they have not found anyone with a weapon.

The alert, issued at 9:37 a.m., said a person possibly carrying a gun had been spotted near Dietrick Hall, a dining area.

Dietrick, a three-story, 93,000-square-foot dining center, also houses a convenience store, laundry area and central bake shop, the Richmond Times-Dispatch notes.

Virginia Tech in Blacksburg, Va., was the scene of a shooting rampage in April 2007 that left 32 people dead and 25 wounded.

The Associated Press says the dining hall is steps away from where the 2007 shooting occurred.

Update at 3:36 p.m. ET: Larry Hincker, assistant vice president of university relations, said the campus alert went about 20 minutes after the two women reported the alleged gunman to police. Officers first interviewed the women to determine whether their report was credible.

The news conference has ended.

Update at 3:32 p.m. ET: Asked about the report of the gun, the campus police chief, Wendell Flinchum, said the two women "described in enough detail that the officers thought it was credible."

Update at 3:27 p.m. ET: At a news conference now, VT spokesman Larry Hincker said all of the university's alert systems "worked without a hitch."

Update at 2:46 p.m. ET: Virginia Tech's website says the alert has been lifted. Here is the message to students issued at 2:41 p.m. ET:

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. While the alert has been lifted, as always, we suggest that people remain vigilant and report suspicious campus activity to Virginia Tech Police.

Update at 1:20 p.m. ET: Hincker says no more sightings of a possible gunman have been reported, nor have any shots been fired, but school officials still are asking students and faculty to stay indoors.

"It's really simply the world we live in today," Hincker says. "You really need to communicate first and investigate later. That's what we did."

Update at 1:13 p.m. ET: Virginia Tech police released a composite sketch based on the reports of a person who may have been carrying a weapon on campus.

Update at 11:59 a.m. ET: The school website says, "Police continue to investigate campus. There have been no other sightings. We ask people to remain secured indoors."

Update at 11:23 a.m. ET: Amanda Huchler, a student on campus, tells USA TODAY's Rachel Roubein that she is among students locked in Hahn Hall. "The professor is still teaching," she says. "Everyone is calm, and no one seems worried. Tech is doing a great job of keeping everyone safe and secure."

Update at 11:12 a.m. ET: Larry Hincker, assistant vice president of university relations, says the report was called in by three people attending a camp called "Higher Achievement." He says there are a number of camps held during the summer at the school, some lasting a few days, others longer. Asked about the status of the alert, Hincker says, "The alert is in effect until further notice. We are asking people to stay indoors until they hear from us again."

Update at 11:09 a.m. ET: Virginia Tech Police Chief Wendell Flinchum says no one is in custody and the alert remains in effect.

Update at 11:07 a.m. ET: At a news conference on campus, a Virginia Tech police official tells reporters that the alert remains in effect.

Update at 10:46 a.m. ET: Here's the school's latest alert:

At 9:09 a.m. three juveniles attending a camp at the university reported seeing a white male, 6 feet tall, with light brown hair outside of New Residence Hall East holding what may have been a handgun. They say the weapon was covered by a cloth or covering of some sort. He was walking fast in the direction of the volleyball courts. He was wearing a blue and white striped shirt (stripes were vertical), gray shorts and brown sandals. The subject had no facial hair or glasses. Officers responded immediately to the area but found no one matching the description. Police have encountered no other witnesses reporting this individual or anything suspicious. Law enforcement officers from VTPD, Blacksburg PD, Christiansburg PD, Virginia State Police, and Montgomery County Sheriff's Office are patrolling the campus, continuing to look for the subject. ... Campus individuals should remain indoors.

Update at 10:35 a.m. ET: John Beck, a student who is not on campus for the summer but receives official communciation from the school, says he got the first text warning at 9:41 a.m. ET.

Update at 10:32 a.m. ET: Law enforcement officers from Virginia Tech, Blacksburg, Christiansburg and Montgomery County were on campus looking for the subject, the Richmond Times-Dispatch reports.

Update at 10:25 a.m. ET: The school's website says three young people attending a camp at Virginia Tech reported seeing a man holding what may have been a handgun, the Associated Press reports.

They said it was covered by a cloth or covering of some sort, and the man was walking in the direction of the volleyball courts.

Lynn Davis, a spokesperson for the school, tells CNN the man is described as a white male with light-brown hair, wearing a blue-and-white striped shirt. He is also wearing shorts and sandals, she says.

Law enforcement officers from Virginia Tech, Blacksburg, Christiansburg and Montgomery County were patrolling the campus, continuing to look for the subject.