This from Scott Peterson:

NEVER FORGOTTEN: January 12, 1951 – Chicago Fire Department, Multi-LODD warehouse fire
Lieutenant John Schuberth Engine 42
Firefighter John P. Gleason Engine 42
Firefighter Henry T. Dyer Engine 11
Chicago Insurance Patrol Firefighter Patrick Milott died a few days later of injuries sustained at the scene. Firefighters were fatally injured in an explosion and subsequent structural collapse while fighting a fire in a four-story office and warehouse building at 320 North LaSalle Street. Seven other firefighters and two civilians were injured by the blast.

The fire began in the lower levels of the 75 year-old building, before spreading through the elevator shafts to the upper floors. The fire was reported to the Chicago Fire Department around 2:04 PM, after which a 5-11 and subsequent special alarms were eventually ordered. The smoke and flames emitting from the structure could be seen for miles around and drew crowds of spectators to the scene.

After burning for thirty minutes, however, the fire caused a substantial explosion that toppled a wall onto firefighters operating hoselines on fire escapes and ladders in an alley outside the building.The special alarms brought 68 pieces of equipment to the site, including all but one of the department’s ambulances. In order to allow the fireboats to navigate the river, the LaSalle Street Bridge remained up for 54 hours as the fire burned.

More than 300 firefighters were on the scene and as many members of the local law enforcement worked to control the crowds. Firefighters stayed on the scene for several days as the fire reignited periodically in the rear area of the wreckage.The explosion was initially blamed on fifty-five gallons of lacquer thinner in storage on the fourth floor of the warehouse, but later investigations showed that the explosion had probably been caused by excessive dust circulating through the elevator shafts. Witnesses later confirmed that the dust contained combustible materials such as paint particles. Property damages from the fire were estimated at $1.5 million.