Police investigate suspicious letter delivered to DuPage courthouse

The DuPage County Sheriff's Office is investigating a suspicious letter that was received Monday afternoon at the DuPage County Circuit clerk's office.

According to a news release, an employee opened the letter about 1:15 p.m. and found an unknown substance enclosed with the correspondence.

The clerk notified deputies assigned to the courthouse, who proceeded to secure the office, officials said.

The Wheaton Fire Department, members of the sheriff's HAZMAT team and Chicago-based FBI investigators responded to the scene and determined, through preliminary tests, that the powdery substance was not harmful.