CALUMET COUNTY, Wis. (WTAQ) - Investigators expect to finish their probe by the end of the month into an explosion that killed a volunteer firefighter in eastern Wisconsin. 33-year-old Steven Koeser died and 8 others were hurt, while putting out a Dumpster fire outside Bremer Manufacturing near Saint Anna. It happened four days after Christmas. Authorities said water from the fire hoses caused a burning container of metal by-products to explode. But we don’t know what caused the container to burn in the first place. Calumet County sheriff’s captain Paul Rusch says they hope to have enough information by the end of February to close the case. The state fire marshal is helping with the probe, along with the U.S. Bureau of Alcohol, Tobacco, Firearms, and Explosives