DNA evidence has now linked two attacks late last year on women near a university campus to the suspected abduction of a third woman on Jan. 20, and authorities said Thursday they're investigating another 2007 case that could be related.

Already linked to a sexual assault in December, police announced that new DNA evidence ties the suspected abduction of Brianna Denison to a third attack in the same neighborhood in November.

They also released a composite sketch of a suspected rapist in a previously unreported attack in the area in October that investigators said is "not inconsistent" with the descriptions in the other three cases near the campus of the University of Nevada, Reno.

The developments stem from an "exponential increase" in information flowing into police tip lines since investigators released a description on Monday of a suspect in a December kidnapping and sexual assault, Reno Police Commander Ron Holladay said.

Police said DNA helped link that crime to evidence collected at the Reno home where the 19-year-old Denison last was seen in the early morning hours of Jan. 20.

On Thursday, police said they also were investigating the October rape of a woman who came forward on Wednesday to report she was attacked at gunpoint in a UNR parking garage within 100 yards of a campus police station.

UNR Police Chief Adam Garcia said the woman decided to contact authorities as a result of extensive media coverage of Denison's disappearance.

Garcia said the latest woman told police she was attacked at about 10 p.m. on Oct. 22 on the first floor of the parking garage just south of the arena where the Nevada basketball team plays.

She said a man "attacked her from behind, knocked her to the ground and held a gun to her head while sexually assaulting her," Garcia said.

Holladay said there's no evidence that connects the October rape to the other incidents but that investigators are "not discounting the possibility these cases may be connected all together."

"Some of the characteristics are similar that she has given, however I wouldn't go as far as to say they are an exact match by any means," he said, adding that "not inconsistent" was an accurate way to describe them.

The new sketch is based on the woman's description of a 5-foot-8 to 5-foot-10 white male with light brown or dirty blond hair. He had a slender to medium build and was wearing a dark-hooded pullover sweat shirt, athletic-type nylon sweat pants with black stripes and white tennis shoes, Garcia said.

The woman described the weapon as a black and silver handgun, the first time police have reported the use of a gun in any of the attacks.

Police did not specify the age of the suspect in the October rape. In the other attacks, victims estimated the age range from 28 to 40.

Dennison, a freshman at Santa Barbara City College in California, was reported missing after spending the night at a friend's home near the UNR campus. A Reno High School graduate, she was back home visiting friends and family during winter break.

Police aren't releasing any details on the DNA matchups, but Holladay said the evidence collected at the scene of the November attack included unopened packages of condoms.

In that case, a female victim was battered and sexually groped on Nov. 13, about 6 p.m., Holladay said. The Trojan brand, lubricated, "very sensitive" condoms in a purple package are "fairly unique," he said, because they first were put into circulation in October or November of last year.

On Dec. 16, another female victim was battered, kidnapped, sexually assaulted and then brought back home by the suspect, he said.

On Jan. 19, the night before Denison last was seen, an unknown suspect returned the home of the victim of the December attack and unsuccessfully attempted to break in, police said.

Police with search dogs and hundreds of volunteers have combed the area daily since Denison's disappearance with no sign of her.

Crime lab technicians earlier determined a small stain on a pillow at the house where Denison vanished is the blood of Denison.

Investigators think someone entered through an unlocked door of the house rented by a Denison friend and three others. Denison, who was sleeping on a couch near a door, was last heard from at 4:20 a.m.

A Denison photo has been featured on casino marquees, fliers and businesses around town.