Sunday night (3/31/19), the Chicago’s MFAO sent companies to a working fire @ 3104 W. Monroe Street. Upon arrival, Battalion 18 had a 3-sty brick, with heavy fire on the first, second, and third floors plus an exposure problem. A Still and Box was requested shortly after. Companies lead out 6+ hand lines and had two truck companies working the roof. For a short time, they had heavy fire venting through the roof and top floor. While working, multiple members fell through a hole in the floor which activated the Mayday Alert and 2-11. I believe the RIT team did remove one of the injured firefighters from the rear of building. Tough fire and a lot of work. Thankfully the injuries sustained were not life threatening. These photos began about 10 minutes into the fire.