The DuPage County Sheriff's Office was at the scene in the Brandywine subdivision in unincorporated Villa Park.
No other information regarding the investigation was released.
At the same time, Villa Park police were investigating a threat at nearby Willowbrook High School.
It was also reported a possible armed suspect may have been on school property.
Bomb threats had been reported at other schools, as well, Villa Park police said.
Students were dismissed early and sent home.
The school was searched and deemed safe, police said.
Police said the two investigations are not connected and there is no threat to public safety.