An open-flame heater on the floor of a rig likely sparked the fire that killed three natural gas drillers and seriously injured two others in a December 2014 drilling rig fire in Coalgate, the U.S. Department of Labor's Occupational Safety and Health Administration has concluded.

In June 2013, OSHA cited the company for allowing the use of an open-flame heater.

The toll

Mark Pittman Jr., Gary Keenan and Kelsey Bellah were working for Dan D Drilling Corp. when the fire erupted. Bellah, 27, and Keenan, 26, died at the scene. Pittman, 26, died from his burns 16 days later in the hospital. Two co-workers suffered serious injuries. One sustained extensive burns to his hands and arms caused by his attempt to assist an injured colleague. He spent a brief time in the hospital. The second man also suffered extensive burns and remained hospitalized until early March.

"Three young men died because Dan D Drilling again allowed the use of an open-flame heater. The heater probably started the fire. The company knew this was hazardous, but chose to ignore the hazard," said David Bates, OSHA's area director in Oklahoma City.

The citations

Based in Lamont, Dan D Drilling received two willful, seven serious and one repeated OSHA violation. The willful violations were for using an open-flame heater on the rig floor that exposed six workers to fire hazards and for failing to provide and ensure that employees were wearing flame-resistant clothing.

The seven serious violations include failing to provide a quick drenching shower for employees who work with corrosive materials; electrical equipment approved for hazardous locations; and training workers on the chemical and physical hazards of new chemicals at the work site.

The repeated violation was cited for failing to provide an emergency egress from the rig derrick platform. A similar violation was cited in March 2013 at a drilling site in Tonkawa.

View the citations at*.

Proposed penalties total $221,200. OSHA has also placed the company in its Severe Violator Enforcement Program. Dan D Drilling, which provides drilling services to the petroleum industry, employs about 270 workers.