The miner killed at Empire State Mines in Fowler earlier this month was struck by material blasted out of a drill hole.
That's according to a preliminary report from the federal Mine Safety and Health Administration.
The report says 40 year old Brendan DeMasters was using a high pressure air hose to clean out a drill hole when he was struck by material forced out of the hole by a sudden release of pressure.
Miners were clearing out a new tunnel in the mine when the October 2 accident occurred.
The report also says DeMasters was a foreman for contractor Major Drilling of Salt Lake City, Utah.
He had more than 20 years of experience as a miner.
A coroner's report a couple days after the accident said DeMasters died of a broken neck.
There were 78 miners underground at the time of the accident.