State police launched a search for 62-year-old Deborah Dewey on Tuesday. Dewey, of Ladd, Ill., was last seen on Aug. 22 in the nearby town of Spring Valley.
A week later, ISP said her gray 2007 Buick LaCrosse was found unlocked at the TA Truck Stop on Route 47 just north of I-80 near Morris.
Investigators searched a residential property near 5th Street and Route 71 in Standard, Ill., on Tuesday for any clues of her disappearance. Several agencies assisted.
State police said Wednesday they found a body buried in a shallow grave on the property. The Putnam County Coroner took the remains to the medical examiner's office in Bloomington, Ill., for an autopsy.
Preliminary autopsy results, which were verified through dental records, indicate the remains are that of Deborah Dewey, investigators said.
Police originally investigated Dewey's death as a homicide, but later said the investigation is a death investigation.
ISP executed a search warrant Wednesday for a nearby house in the 200-block of 8th Street. Officers interview three people who live in the home and gathered evidence.
Clifford Andersen, 66, of Standard, was arrested and charged with concealment of a homicidal death. He is being held at Bureau County Jail on $750,000 bond.
Anyone with information regarding Dewey's death should contact ISP District 17 headquarters at 815-224-1171.