RANSOM, Ill. (CBS/WBBM) – With the search for a missing LaSalle County woman at a standstill, the sheriff says his investigators are talking to relatives, friends and acquaintances about what may have happened to 40-year-old Tanya Shannon.

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Airplane. Helicopter. Thermal imaging. Dogs. People on foot and on ATVs. All searching around the car crash site for Tanya Shannon. And nothing found, says Sheriff Tom Templeton.

Dale And Tanya Shannon: Car Crash

The crash scene. (LaSalle County Sheriff' Photo)

“After a search for three-and-a-half days with everything that we used to search, we have just not been able to find Tanya. So the only plausible alternative to that is that Tanya isn’t there and got picked up on the road by someone at some time before our deputy arrived.”

Sheriff Templeton says that may seem like the only plausible alternative but he’s not ruling out the possibility that search crews missed her – and her red dress – in the snow-covered fields.

“On the street, as we speak, doing interviews. You talk to friends. You talk to relatives. You talk to acquaintances. You talk to people. We’ll never get any answers unless you’re talking to people. And so they have been and they will continue to do that.”

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Among the questions for which investigators are seeking answers is the whereabouts of Dale Shannon’s cell phone. Templeton says Tanya’s cell phone was found in the car, but Dale’s is still unaccounted for.

Shannon, a mother of four, vanished after the car crash that killed her husband early Sunday.

Dale And Tanya Shannon: Car Crash

Dale Shannon was killed in a car crash over the weekend, and his wife, Tanya, is still missing. (Credit: LaSalle County Sheriff's Office)

Tanya Shannon, of Ransom, Ill., was last seen leaving a friend’s holiday party wearing a red dress and was believed to be riding with her husband when their car crashed a short time later as it snowed. A LaSalle County sheriff’s deputy found the wreck along a well-traveled stretch of highway. Dale Shannon, 41, was dead behind the wheel and footprints led away from the car.

The coroner of LaSalle County says Shannon died of a broken neck early Sunday morning when the car he was in hit a utility pole.

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Due to cold conditions, Templeton said Wednesday that the search for Tanya Shannon would be suspended for “probably the next several days.”