Tanya Shannon, 40, disappeared after a car crash in LaSalle County after leaving a Saturday night party.
Her husband, 41-year-old Dale Shannon, was killed in the accident in rural Brookfield Township. Preliminary autopsy results indicate he died of spinal injuries.
LaSalle County Coroner Jody Bernard says the injuries to Dale Shannon are consistent with a rear-end collision with a utility pole. Bernard tells WSPL Radio that toxicology reports could come next week.
Tanya Shannon, of Ransom, Ill., was riding in the car that crashed early Sunday morning. Footprints were spotted in the snow near the car, but the mother has not been seen.
Aircraft and sonar imaging have been used in the effort to locate the 40-year-old woman, but the search has not yielded any significant clues.
Investigators say their hope of finding Shannon alive has begun to fade.
"Realistically, we have to be looking at it as a recovery effort, if she's in fact out in the elements and outside," said Sheriff Tom Templeton, LaSalle County.
On Tuesday, police and firefighters scoured frozen farm fields for a third day hoping to find any trace of Shannon. More than 35 searchers carefully scanned the area near the crash site. With temperatures hovering around 20 degrees, searchers on foot went out for only an hour at a time, coming back to a command center to warm up and get their blood pressure checked.
The clues surrounding Shannon sound like the makings of a fairy tale: a red dress, a lone slipper, footprints in the snow. For friends and relatives, however, they're the makings of a nightmare.
Shannon was last seen leaving a friend's holiday party in her red dress and was believed to be riding with her husband when their car crashed a short time later as it snowed. A deputy found the wreck along a well-traveled stretch of highway early Sunday. Dale Shannon was dead behind the wheel and footprints led away from the car.
Other than the slipper found a short ways away, there has been no other sign of Tanya Shannon. She had apparently changed out of her heels for the ride home.
"It's just one of those weird situations," said Sergeant Jeff Whalen of the LaSalle County Sheriff's office. "We have no idea what happened."
Before the foot search was suspended Tuesday evening, dozens of people braved frigid temperatures for a third day to scour an area just miles from the couple's home in Ransom. They probed snow banks with poles, operated metal detectors in ditches and even used a helicopter over the flat, snow-covered landscape about 70 miles southwest of Chicago.
Authorities say Shannon, a part-time waitress, may be dead and her body may be buried in the snow, but they also haven't ruled out the possibility that she's still alive. Authorities believe Shannon may have tried going for help and could have been picked up along the road.
"We just want her home," said Shannon's sister Corinne Johnson of Ottawa. "I just want to find her."
Johnson said she last heard from Shannon through a text message around 9:45 p.m. Saturday when Shannon was apparently at the party. It read, "I can text ya 2morrow at dales xmas party all dressed up."
Johnson said she and her sister talked about the condition of the roads before the party, and that Shannon said she wasn't afraid to drive, especially since she had lived in Illinois for twenty years.
At first, Johnson said she thought the disappearance was due to "something silly." But she said she changed her mind as crews searched for a third day Tuesday without finding any clues.
"I wasn't thinking something drastic like this," Johns said. "She just wouldn't walk away from this, this is her life."
The couple's four children -- who range in age from 4 to 15 years old -- are in the care of family.
"The kids are doing as well as expected," Johnson said.
The Associated Press contributed to this report.