Investigators trying to find Virginia Tech student Morgan Harrington said their scrutiny of surveillance video from the area around the John Paul Jones Arena in Charlottesville -- where the 20-year-old disappeared -- has ended in frustration.

The footage has not yielded any clues to the Roanoke County woman's disappearance, said Corinne Geller, spokeswoman for the Virginia State Police.

"We've looked at all the surveillance video -- gas stations, convenience stores, ATMs -- any camera in that immediate area has been looked at," Geller said. "Nothing in the videos is relevant to the case."

Meanwhile, the FBI has joined the investigation.

Harrington vanished Saturday while attending a Metallica concert with friends. Her friends told investigators she left them sometime that night to go to a restroom and wound up outside the arena, which has a no-readmittance policy. Harrington called her friends to say she would either meet them after the concert or find another way home.

Her purse and cellphone were found the next day between the arena and an athletic field. Harrington, who has blue eyes and blond hair, stands 5-foot-6 and weighs 120 pounds. She was last seen wearing a black miniskirt, a black T-shirt with the name of metal band Pantera across the front, black tights and black knee-high boots.

"We just do not know at this point what has happened to Morgan," said Lt. Joe Rader of the state police on Wednesday. "Somewhere out there there is still very vital information that we need to get that we have not yet received."

State police have set up a tip line at (434) 352-3467 and offered a reward that Harrington's father said now stands at $100,000.

Geller said investigators contacted the task force looking into the slayings of Virginia Tech students Heidi Childs and David Metzler, who were shot to death in August at a campsite in the Jefferson National Forest in Montgomery County. However, she said, investigators have concluded the killings are not related to Harrington's disappearance.

-- Rex Bowman