A worker found the body about noon in a brush-covered field on the city's south side near a light industrial area, Reno police spokesman Steve Frady said.
"There has been a lot of speculation, a lot of rumor about a possible connection with the disappearance of Brianna Denison. At this point we have no information to link that case with this one," Frady said at a briefing.
About 45 law enforcement and crime lab personnel, including three FBI agents, remained at the scene before night fell.
Frady said the time and cause of death would be determined by an autopsy scheduled Saturday. Authorities have "no ID, not even a tentative ID," he said.
"I'm not going to speculate because we don't know who the person is," Frady said.
"We're processing this as a crime scene. We do that with death investigations," he told The Associated Press. "They are gathering information and evidence and photographing the area."
Investigators have not indicated whether they believe the woman died from natural causes or was slain, Frady said.
"We don't know how long the body has been out there. It's definitely a female. We don't know the age," he said. "It's really not the time to speculate. This is a time for fact finding."
Crime lab technicians gathered evidence from the body as about a dozen officers walked in straight lines doing a grid search in the vacant field grown over with waist-high brush and weeds. Investigators cordoned off about half of the five-ace field.
"Obviously, we want to comb every inch of ground for any clue that may help tell the story what happened here," Frady said.
Washoe County District Attorney Dick Gammick also was on the scene.
The body was removed about 4:30 p.m. and taken to the Washoe County Coroner's Office, Frady said. He said he did not anticipate investigators would release any additional information Friday night.
Denison was abducted Jan. 20 by a serial rapist linked by DNA to a string of attacks near the University of Nevada, Reno campus.
Denison, a student at Santa Barbara (Calif.) City College who was visiting her hometown over winter break, was last seen sleeping on a couch at a friend's off-campus rental house.
Police have said DNA evidence links Denison's kidnapping to two other attacks on women near the university late last year, and that an earlier on-campus attack also could be related.
A worker from a nearby business spotted the body while walking back from lunch and told a supervisor, who telephoned investigators.
The field is within a light industrial park with commercial office buildings and businesses. It's bordered by an upscale neighborhood about eight miles south of the home where Denison last was seen.
Associated Press Writer Martin Griffith also contributed to this report.