The owner of a Mount Maunganui timber manufacturing business watched in horror as two of his workers ran towards him on fire after an explosion on Thursday.
Graeme Woolley, whose Trayco factory produces wooden crates and boxes, says the explosion was in the container of a machine that extracts sawdust from his factory.
Mr Woolley says he smelled smoke coming from the machine and told his employees to shut it down.
"While we were waiting for the system to shut down, the system exploded. We've checked since but found there was a piece of plastic jammed in the rotor of the fan, and (it) must have caused a spark and ignited the dust inside the container."
He says the injured workers are in hospital, one with serious burns.
Firefighters quickly controlled the fire at the Hocking St site after being called at 11am.
The Department of Labour has started a preliminary investigation into the explosion.