The disappearance of a Virginia college student last seen at a heavy metal concert remained a mystery Thursday as state police said they had no evidence to prove one way or the other that Morgan Harrington is the victim of a crime.

Harrington, a 20-year-old junior at Virginia Tech in Blacksburg, hasn't been seen since Saturday night when she was separated from her friends at a Metallica concert in Charlottesville.

Virginia State Police said that though they are treating the case as a criminal investigation, they haven't found conclusive evidence about whether or not a crime was committed.

SLIDESHOW: Morgan Harrington Vanishes at Concert

"At this point, we don't have anything to indicate that foul play was involved — although we don't have anything to say it's not," state police spokeswoman Corinne Geller told FOX News Thursday.

"We're treating this as a criminal investigation only because that's the way we need to go into this to make sure we've got every base covered."

Geller said police are sifting through at least 130 leads that had come in as of Thursday morning.

"We have been flooded with tips," she said. "Hopefully, one of those will be the missing link we need. We’re still very hopeful that we will locate her, that she will turn up safely and that we’ll have a peaceful resolution to this."

Harrington's family said they're trying to stay composed.

"I’d like to go upstairs and hide under the duvet right now and tell the world to go away," her mother Gil Harrington told reporters. "But we have to be strong right now and keep doing whatever we can do just like we want her to be strong and do what she can do."

Authorities have asked Metallica fans to check video or photos taken at the concert for signs of the missing student, an education major.

Lt. Joe Rader of the Virginia State Police Department said Harrington left her friends at the John Paul Jones Arena to use the bathroom but somehow wound up outside and couldn't get back in.

The facility doesn't allow anyone to re-enter once they've left the premises, he said.

Harrington's college roommate, Amy Melvin, told The Roanoke Times that her friend walked out of the stadium before Metallica appeared on stage, but she didn't know why.

Rader said Harrington then called her friends to let them know she wouldn't be coming back, and disappeared sometime after 9:30 p.m.

A passerby found her cell phone and purse in a small parking lot near the arena Sunday morning, Rader said. An extensive ground search ended late Wednesday.

Harrington's distraught parents said they usually talk to her every day and her disappearance is completely out of character.

"Morgan is a pretty transparent kid, who's had a really close relationship with us," her father, Dan Harrington, said in a phone interview Tuesday with The Associated Press. "I don't think there are lots of secrets, so this kind of behavior of (her) missing is not something I think we would expect."

His daughter doesn't have a boyfriend, he said, and he couldn't think of anyone who'd want to hurt her.

Police said Morgan Harrington was last seen wearing a black "Pantera" T-shirt, a black mini skirt, black tights and black knee-high boots.

She has long blond hair and blue eyes, is 5-foot-6 and weighs about 120 pounds.

Anyone with any information about Harrington's disappearance is asked to call the police tipline at (434) 352-3467.

The Associated Press contributed to this report.