MONACA, Pa. (AP) -- The U.S. Chemical Safety Board says a column used to distill zinc in a western Pennsylvania plant had failed before an explosion killed two workers on July 22.
The federal board is investigating the explosion at the Horsehead Corp. plant in Potter Township, about 25 miles northwest of Pittsburgh. The company, its union and the federal Occupational Safety and Health Administration are also investigating.
The chemical board doesn't issue fines, but is empowered to make safety recommendations. On Tuesday, the board says it determined that the five-story brick distillation column suffered a "loss of containment" before the explosion.
When operating normally, natural gas and carbon monoxide are used to oxidize molten zinc as it flows through the column.
Horsehead spokesman Ali Alavi says "it's too early to speculate" on the board's findings.