Authorities showed up to a home near Warrington Road and Cumberland Parkway in Des Plaines on Monday morning around 7 a.m., neighbors told ABC7 Chicago.
On Wednesday, Des Plaines police revealed they are conducting a follow-up investigation to an "old case."
Neighbors said officers have been in and out of the backyard of the home.
"Contrary to some reports, investigators are not searching for a body at this residence," police said.
It's unclear what exactly they're searching for, or rather, what they may have already found.
Neighbors told ABC7 that three generations of a family live at the home and have lived there for a while.
SEE ALSO: Portage police find remains of Hobart woman missing since summer 2020
Investigators were seen concentrating on the driveway of the home, and some were seen looking closely in the backyard.
With the crime scene van parked in front for a third day in a row, some neighbors are uneasy.
"It's scary. How did they come to the conclusion it was this? They musta got some lead that brought them here," neighbor Jeanette Sedano said.
Des Plaines police said there is no threat to the public.
At one point Tuesday, they brought in dogs to help.
"You see all this activity, the crime scene tape, bringing in equipment," neighbor Irma Dzik said.
The Cook County Major Case Assistance Team is involved in the investigation.
Police say they are unable to release information about what they are looking for without jeopardizing the investigation.
A 36-year-old man who lives at the house is currently in jail awaiting trial on numerous felony charges, including armed robbery, kidnapping and aggravated battery. But police declined to say whether their search of the property is related to his case.
"They're digging. Them saying they're not looking for a body, yet they bring in dogs. You just wonder, wonder what's really going on," Dzik said.