Read fire marshal's report into dumpster explosion that killed Wisconsin firefighter Steven Koeser.

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From PostCrescent.com:

WI St. Anna Steven KoeserAn explosion that killed St. Anna firefighter Steven Koeser and injured eight others Dec. 29 was caused when firefighters sprayed water and fire-suppressant foam into a burning trash bin.

A news release issued today by the state Department of Justice Fire Marshal’s Office and the Calumet County Sheriff’s Department said the trash bin contained aluminum alloy shavings and 55-gallon steel barrels of aluminum dross (slag).

The origin of the fire in the trash bin at Bremer Manufacturing Co. in the Town of New Holstein was found to be undetermined, investigators said.

Volunteer firefighters responded to the scene after a sheriff’s deputy reported a fire in the trash bin that appeared to be melting the container. Bremer was closed at the time.

Above are the St. Anna Fire Department radio transmissions from December 29, 2009. Click here for the radio traffic from the Calumet County Sheriff’s Department.

When firefighters arrived on scene, flames were visible from the trash bin.

Seventeen firefighters were within 50 feet of the trash bin when the explosion occurred. The thunderous blast was heard miles away. Koeser, 33, of Kiel was operating a pump near the trash bin. He was a 15-year veteran of the St. Anna Fire Department.