Police searching an area about 10 miles south of Madison found the body on private property in a wooded area dotted with homes. Dane County Coroner John Stanley said it was tentatively identified as 22-year-old Kelly Nolan, and Madison Police Chief Noble Wray said the case is being investigated as a homicide.
CBS News affiliate WISC-TV reported that with the discovery of the body about 8:45 a.m., the search was being called a homicide investigation, according to police spokesman Joel DeSpain.
Formal identification may not come until Tuesday or Wednesday. Investigators have yet to get a "detailed, up-close" look at the body, which was covered up in a densely wooded area, but preliminary evidence suggests it is Nolan, Stanley said.
DeSpain declined to describe the condition of the body but said it was obvious to detectives that the person had been killed.
Chief Noble Wray said cell phone technology led police to the area around Fitchburg, where the body was found, but declined to elaborate. Police said they have not recovered Nolan's cell phone.
"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 identified 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 a group of friends that included her sister before midnight.
Police have interviewed people who saw and spoke with Nolan at several downtown bars after that. She also spoke to her sister by phone after midnight.
A cafe employee reported seeing Nolan early 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, authorities said.
Nolan's sister April, 20, described her 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 offered a $10,000 reward for information leading to her return.