Suspicious envelope found at Cook County building next to Chicago City Hall, prompting hazmat response

A suspicious envelope found at the Cook County building, next to Chicago City Hall in The Loop, prompted a hazmat response on Thursday morning. 

The Chicago Fire Department said a level 1 hazmat response was initiated at 118 North Clark after the envelope was found.

A large emergency response was at the scene, but it does not appear that the building was evacuated. 

No further details were released. The incident remains under investigation. 

Federal authorities are currently investigating letters with "suspicious substances" that have been mailed to congressional and election offices nationwide. 

The investigation by the FBI, U.S. Postal Inspection Service and U.S. Capitol Police was first disclosed in a message from the Senate Sergeant at Arms obtained Thursday by The Associated Press. The notice, sent to Senate offices, said that law enforcement officials were working to intercept any additional letters, but "it is possible that some letters may reach their destinations."

The large building that houses Chicago City Hall also houses Cook County government offices, including the treasurer's office, the assessor's office and Cook County Board offices.

Fire officials said at this time there was not a bona fide threat at the Cook County building. 

Please note: The above video is from an earlier report.