From an article by Tom Kertscher in the Milwaukee Journal Sentinel:

Oak Creek – An explosion Tuesday morning inside a We Energies coal dust silo rained flames down on a group of contract employees who were making preparations for repair work to begin.

Four employees were inside the 65-foot-tall structure and two outside when the explosion occurred, said a We Energies spokesman. A doctor said a 43-year-old man pulled his son, 22, and at least one other co-worker to safety.

The 22-year-old was the most severely injured, suffering burns to more than half his body, according to Tom Schneider, medical director of the Columbia St. Mary’s Regional Burn Center in Milwaukee.

The cause of the blast, reported at 10:53 a.m., has not been determined. Federal and local authorities will be investigating, officials said.

The six workers are employees of the Milwaukee branch of ThyssenKrupp Safway, a Waukesha-based company that provides scaffolding services, said Michelle Dalton, a company spokeswoman. She would not identify the workers.

ThyssenKrupp was hired as a subcontractor by United States Fire Protection, a New Berlin firm that provides fire protection services, according to We Energies spokesman Brian Manthey.