Federal investigators say a factory explosion that fatally injured seven workers in Kentucky earlier this year was probably caused by a fire in a malfunctioning production line oven that ignited flammable dust particles.

Dr. Jerry Poje, a member of the U.S. Chemical Safety Board, says the accident came less than a month after a similar blast at a Kinston, N.C., plant killed six people. The Kinston explosion, and lesser ones in California and Mississippi, are believed to have been caused, at least partly, by flammable dust that exploded, he says.

Workplace safety experts are increasingly concerned that flammable dust in factories represents the same kind of danger identified two decades ago in grain elevators, according to Poje. Safety standards were adopted after deadly explosions were linked to combustible dust in the silos.

“Preventing industrial dust explosions is probably our biggest priority right now,” beyond finding out exactly what happened in the two major explosions, Poje told neighbors of the Kentucky plant at an open meeting.

The U.S. Chemical Safety Board does not set standards, but it is expected to make safety recommendations to all manufacturing plants where combustible dust could ignite by the end of the year. It might also recommend to OSHA ways of strengthening federal regs for handling industrial dust.