Charleston, W.Va. ? State investigators said missing walls that control air flow and faulty firefighting equipment were key factors in the deaths of two miners in a conveyor belt fire at an underground coal mine in January.

Investigators concluded the missing walls allowed smoke to enter the main escape route at Massey Energy Co.’s Aracoma Alma No. 1 Mine, the Office of Miners’ Health, Safety and Training said in a report released Thursday.

The agency also determined the mine was not following its approved ventilation plan.

The investigation also found that water lines for fire hoses and sprinklers at the scene of the fire were shut off and that fire hoses at the site couldn’t be connected because of incompatible fittings, a problem that had been reported to management after a similar fire on Dec. 23.

Investigators said the fire resulted from a misaligned conveyor belt that carries coal. The belt was rubbing a bearing, causing friction. Mine personnel could not fix the alignment problem before the evening shift started, but operated the belt anyway, according to the report.