RENO, Nev. -- Search dogs will be used by the Reno Police Department at about 4:30 p.m. Tuesday to comb the neighborhood around the Mackay Court residence where 19-year-old Brianna Denison was staying Sunday morning when she disappeared.

The area has already been searched by dogs, including an extensive search of nearby Rancho San Rafael Park with the use of helicopters and police K-9 units, and a canvas of the neighborhood by police officers distributing fliers with Denison's photo and speaking with neighbors, said police.

Police detectives said they wanted to search the area again before anticipated snowstorms occurred.

Denison was in Reno visiting her family during a winter school break and was scheduled to return to classes at Santa Barbara City College Tuesday. She was reported missing Sunday by a friend with whom she was staying the night at 1395 Mackay Court.

Her friend, K.T. Hunter, said that when he awoke, she was simply gone. Hunter said only left behind a spot of what appeared to be blood.

"She wasn't there and I noticed blood on the pillow so we called the cops. From then, it's just been a nightmare," said Hunter.

Denison was described as white, approximately 5 feet tall, with long dark brown hair and blue eyes and weighing about 98 pounds.

She was last seen wearing pink sweatpants and a white tank-top shirt. While a 24-inch brown stuffed bear with white and multi-colored balloons on its belly was missing from the area where she was sleeping, her cell phone, purse and clothing, including two pairs of shoes, were left behind.

Earlier Tuesday, police confirmed the Federal Bureau of Investigation had officially joined the investigation into Denison's disappearance and probable abduction.

Tuesday afternoon, two investigators from the National Center for Missing and Exploited Children also joined the investigation.

A 24-hour tip line has been established by the Reno Police Department to gather information from the public at 775-745-3521.

Information can also be called into the Secret Witness Program at 775-322-4900, or the Reno Police Department Detective Division at 775-334-2115.

Reno police detectives are still seeking the driver of a beige or light brown Chevrolet or GMC Suburban-style SUV, who provided a ride to the Mackay Court address for a friend of Denison's who lived there, to determine if he saw anything unusual.

The driver of the vehicle is considered to be a person of interest who may have information that could assist with the investigation.

He is described as being white, possibly of Latin descent, about 45 years old, of medium stature and well-dressed. The vehicle was photographed by security cameras as it left the Sands Regency Casino & Hotel via the Arlington Street driveway.

Police are also awaiting results of tests conducted on a silver dollar-sized spot that potentially could include blood found on a pillow Denison was using before she went missing.

Detectives also said Tuesday there does not appear to be a connection between Denison's disappearance and two assaults on female college students near the University of Nevada Reno campus late last year.

They said that Denison was having a text-message based fight with her boyfriend, but added that he is not a suspect. They said he was in Oregon at the time of her disappearance.

Family members said that other terrifying questions are still bubbling to the surface.

"What scares me is, like, the dog not barking. Did he know that person that came in? Did they sleep through a dog barking? Why did Brianna not scream?" said Rena Denison, Brianna's aunt.

Denison was slated to return to school in Santa Barbara Tuesday after the visit. Her family is offering a $100,000 reward to get her home safely.