McFarland's police chief says the couple found dead in a burned out car early New Year's Day never attempted to get out of the vehicle.
McFarland Police Chief Craig Sherven said that indicates the couple may have been asleep or overcome by carbon monoxide as fire burned the car.
"I would say that's a very plausible explanation, that in a small contained area such as inside of a vehicle cabin that somebody could be rather quickly overcome by carbon monoxide," Sherven said.
The deaths Brandon Slattery, 24, and Amy Damon, 21, both of Edgerton, have been ruled accidental.
"If the fire were to have started in the engine compartment and started out slowly, this was a very cold night so obviously the heater would have been going, blowing air from the engine compartment potentially into the cabin area of the vehicle," Sherven said.
Toxicology results would also show carbon monoxide levels. Those results should be available in about four weeks.
Sherven said there's no indication of foul play. The chief said Slattery and Damon appeared to have been sitting in the front seats.
Funeral services for the two were held Monday.
Slattery and Damon became engaged this past summer and had plans to get married later this year, according to friends and family.
Sherven said the couple lived in Edgerton and traveled to McFarland with a friend, in the friend's car, for a New Year's Eve gathering.
At around 5 a.m., Slattery and Damon left the New Year's Eve gathering to go back to their home in Edgerton, police said. The owner of the vehicle gave them permission to drive his car home as he wanted to stay, police said.
Police said the couple traveled about a block and a half and pulled over near the intersection of Holscher Road and Prairie Wood Drive. Police aren't sure why the couple pulled over.
According to witnesses at the party, it didn't seem as if Slattery and Damon were impaired, so pulling over because they realized they were too intoxicated to drive doesn't appear to be the case, according to Sherven.
Sherven said police are awaiting toxicology results, which could take a month.
At 6 a.m., firefighters received a report of a car on fire. As authorities arrived at the scene, they saw the car fully engulfed in flames.
Police said it wasn't until after firefighters got the fire out that they discovered Slattery's and Damon's bodies inside.
"The flames were such that when the officer arrived, you couldn't even approach the vehicle -- the heat emanating alone, without proper gear, you couldn't even get near it to look into it or try to do anything with it," Sherven said Wednesday.
Police said it appears the fire started somewhere in the front of the vehicle, presumably the engine compartment, but at this point, investigators are not 100 percent certain.
The case remains under investigation by the Village of McFarland Police, the State Fire Marshal's Office and the Dane County Medical Examiner's Office.
Damon was a nursing student at Madison College. Becky Zarling, one of Damon's classmates in the nursing program, said she and her other classmates are devastated by the loss.
Zarling said Damon was not only caring but she also kept the class going and motivated when things were getting tough.
"Amy is definitely a morale builder -- her smile was just infectious. She could make anyone in the room smile. She never had a bad word to say about anyone or anything. She had the biggest heart," Zarling said.
Slattery also attended Madison College in the auto technician program. He worked at a Zimbrick dealership in Madison.
As construction continues on Madison College's new Health Sciences Learning Center, classmates are working on creating a permanent memorial in Damon's honor.
They're raising funds to build a bench at the entrance of the new building to keep Damon's memory alive. To support the project, people can make a donation for the bench by visitingwww.madisoncollegefriends.org/donations/ and clicking on the link for the "Amy Damon Memorial Fund."