An oil field rig exploded in West Texas in March, killing three workers, according to the Associated Press.
Investigator Dusty Kilgore of the Upton County Sheriff's Office told AP the accident happened about 40 miles south of Midland.
A pulling unit crew was at the site when the explosion happened. OSHA describes a pulling unit as a well-servicing outfit.
Kilgore told AP one other worker at the site was not hurt in the explosion. He didn't release to AP the names of those killed.
The well is owned by Parsley Energy of Midland. Company spokeswoman Lisa Elliott told AP the workers who died were employed by Mason Well Service Ltd. of Odessa, an independent contractor.