When firefighters poured water into a Searsmont lumber yard silo, they were unknowingly adding fuel that helped cause the mill’s deadly silo explosion back in May. The report, released Friday, found a series of missteps from area fire departments and Robbins Lumber itself that contributed to the tragedy. This silo, which Robbins Lumber bought used back in 1993, was sealed to keep out oxygen. Unbeknownst to firefighters, they were adding oxygen and stirring up dust suspended in an “explosive mixture,” according to the report. Robbins Lumber is a leading supplier of eastern white pine products, with roots in Searsmont that stretch back nearly 150 years.