Investigators believe a female body found Monday is that of a college student who vanished last month after a night out at the bars in Madison.

Police searching an area 10 miles south of Madison found the body on private property in a heavily wooded area dotted with homes.

Dane County Coroner John Stanley said the body was tentatively identified as 22-year-old Kelly Nolan, and Madison Police Chief Noble Wray said the case had changed from a missing-persons investigation into a homicide probe.

A formal identification may not come until Tuesday or Wednesday. Stanley said investigators had yet to get a "detailed, up-close" look at the body, which was covered up in a very densely wooded area, but preliminary evidence suggests it is Nolan.

Police spokesman Joel DeSpain declined to describe the condition of the body, but said it was obvious to detectives that the person had been slain.

Wray said cell-phone technology led police to mount a massive search Monday morning in the area where the body was found. The search focused on a 3-square-mile area around Fitchburg that included part of the neighboring village of Oregon, just off U.S. Highway 14.

Investigators were taking their time with the search for evidence because the area was so large and the death scene was described as complex. Stanley said investigators haven't even touched the body yet.

"The cover is fairly thick," he said. "It's another reason that we have to move slowly. There may be things that we might step on or disturb by just going in there."

DeSpain said that he was not aware of any specific suspects in Nolan's disappearance and that the area was one of several areas identified during the investigation as worth searching.

Nolan, a University of Wisconsin-Whitewater student from the Madison area, had been living in a Madison apartment for the summer and was last seen early June 23 after a night out with friends at bars.

She left the group before midnight.

Police have interviewed people who saw and spoke with Nolan at several downtown bars after that. Nolan also spoke to her sister by phone after midnight.

A cafe employee reported seeing Nolan early on June 23 and walked her toward her home until they ran into another man who said he knew Nolan, according to Tom Paras, the owner of Amy's Cafe.

Two days later, when the employee learned of Nolan's disappearance, he called police with the information, Paras said.

Police said the area where the body was found had been searched before, but not to the extent it was on Monday morning. Dogs trained to recognize Nolan's scent were involved in the latest search, which also involved more than 100 police officers, several agencies and volunteers.

The area is well-known to people who ride horses in the area, DeSpain said.

Nolan's sister, 20-year-old April, described Kelly as fun-loving and creative, but said she had been going through a tough time since the deaths of their father in 2006 and their stepmother in May.

Nolan didn't get the summer job she had hoped to find when she returned from school, and she had worked at a restaurant for about a week in June before being fired the Wednesday before she disappeared.

In the spring, Nolan served 14 days in jail after pleading guilty to driving under the influence as a second offense.

Nolan's family announced a $10,000 reward for information leading to her return. But family members stayed out of the spotlight on Monday.

Nolan's disappearance evoked memories of another woman, Angela Drake, who disappeared after going home with a man she met in a Fitchburg bar in 2005. Her body was found frozen in a culvert.

Michael Desalvo, the man Drake left with, is serving 25 years in prison for her death.

Monday's news conferences were held in the basement of Holy Mother of Consolation church in Oregon, where Drake's family attends Mass. Pastor Bill Connell said the Drakes were in church Sunday praying for the Nolan family.

"We went through this two years ago with Angela Drake's murder," said Connell, who performed Drake's funeral. "It's a tragic experience. There's no explanation for it. But when the community gathers around, that's a sign they're giving support at a critical time."