The smoke detectors were working, and neighbors called police when they heard the alarms, said Menomonie Police Chief Dennis Beety. Police don't know why the three victims didn't wake up and leave.
"There was a bottle of alcohol and the top was off of it," Beety said. "But that's no indication they were drinking at the time."
The university identified the victims as April C. Englund, 21, of West St. Paul, Minn.; Amanda Jean Rief, 20, of Chaska, Minn.; and Scott A. Hams, 23, of Hayward. All three appeared to have died of smoke inhalation, said authorities, who do not suspect foul play.
"It's a tragedy that no campus prepares for," Chancellor Charles Sorensen said. "We'll grieve in this together."
Firefighters arrived five minutes after a call made about 3:30 a.m. to find smoke coming from the basement, first floor and second floor of the duplex, university spokesman Doug Mell said.
Englund was the only resident of the front unit of the white house in a row of well-kept properties blocks away from campus. The other two victims -- Rief and Hams -- were sleeping over because Englund's roommates left town, Englund's father and authorities said.
All three victims were found in separate bedrooms.
University counselors were on hand to help students, and the school encouraged students to call their families.
Hams had pictures online of him water skiing, doing stunts with a motocross dirt bike and flying a small airplane. He said he liked snowboarding, wakeboarding and skateboarding.
"I can't believe it's real," said his father, Allen Hams. "I know there's a reason. God's got a plan. He's such a good kid; he'd do anything for anybody."
The elder Hams said he had talked to his son on Friday night.
Scott Hams, who was to graduate in May with a degree in business administration with an emphasis on risk control and had an internship lined up, had wanted to take his motorcycle back to campus since the weather had gotten warmer.
"He called nearly every day," he said.
Hams, who has a 14-year-old brother, lost his mother to cancer three years ago.
"The police came over with the pastor and I said, 'What's going on here?"' Hams said. "They told me to sit down, and then we all had a good cry together."
Englund, a senior, was majoring in retail merchandising with a minor in business. Bill Englund said his daughter had worked at a women's clothing store for five years.
"She loved it. She loved fashion, colors, design," Englund said. "She studied to do that. She was already promised a job when she graduated next year."
One of the family's highlights every year was a canoe trip that included her 80-year-old grandmother.
"She looked forward to that every year, being with family, being out in the woods," Englund said. "She was a city girl otherwise."
Reif was a sophomore majoring in business administration. A woman who answered the phone at Rief's home in Chaska declined to comment, asking for privacy.
In a letter to students posted on the school's Web site, Soreson wrote: "Our hearts go out to family and friends of these students. The whole campus is grieving for the loss of these fine young people."
The school of 8,400 students is about 70 miles east of Minneapolis.