A hazmat response was underway Thursday at the Cook County Building at 118 North Clark, next to Chicago City Hall, after a suspicious envelope prompted the call. The response was classified as Level 1, and officials had not released further details as of Thursday afternoon.
The Chicago Fire Department confirmed the situation was classified as a Level 1 hazmat response, according to CBS News Chicago, which reported the story was still developing as of Thursday afternoon. The outlet, citing CBS Chicago digital producer Elyssa Kaufman, said a suspicious envelope prompted the response at the Cook County Building, 118 North Clark, next to City Hall, and officials had not released further details. In Chicago Fire Department operational terms, a Level 1 hazmat designation represents the baseline dispatch level for suspected or potential hazardous material incidents, reserved primarily for investigative activity or low-risk material containment, according to Firehouse Magazine. That tier of response typically sends a battalion chief, an engine, a truck, and a Hazardous Incident Team task force that includes a squad unit.
A Department Built for This
Chicago's fire department is the second-largest municipal fire department in the country and maintains two specialized Hazardous Incident Team units, designated 5-1-1 and 5-1-2, to cover hazmat and chemical emergencies across the city's 228-square-mile footprint, per Firehouse Magazine. The magazine reported that the units were placed into service in January 2004.
Thursday's call unfolded at the Cook County Building, next to one of Chicago's most consequential municipal buildings. City Hall at 121 N. LaSalle St. is a 12-story Classical Revival structure completed in 1911, next to the Cook County Building at 118 N. Clark St., according to Wikipedia. The LaSalle Street side houses the fifth-floor executive offices of the Mayor of Chicago, the City Council chambers, the offices of the city's 50 ward alderpersons, the City Clerk, and the City Treasurer, a layout that Clio describes as making the address the core legislative and executive headquarters for municipal government.
Not the Building's First Emergency Scare
City Hall has weathered emergency incidents before. In December 2024, City Hall and the adjacent Cook County Building were evacuated after a paper-products fire broke out on the third floor while members of the City Council were meeting inside, Fox 32 Chicago reported; no hospital transports were reported. Less than a year later, in November 2025, a small fire outside City Hall prompted a police arson investigation, according to the Hoodline article covering the incident at the time.
CBS News Chicago said it would continue providing updates as the situation at the Cook County Building develops.
