CHARLESTON, W.Va. -- Federal regulators have cited the employer of a worker who was killed earlier this year in explosion at a natural gas production site in Taylor County, records show.The U.S. Occupational Safety and Health Administration issued one serious citation to Central Environmental Services LLC following its investigation of the Feb. 15 death at a site near Flemington.Brian Hopkins, of Little Hocking, Ohio, died in the explosion, which occurred at an EQT Corp. well site, according to records from OSHA and the West Virginia Department of Environmental Protection.DEP officials said at the time that the incident appeared to have occurred while Hopkins was attempting to transfer briny wastewater from an onsite tank to a truck that would haul the material to a disposal site. Central Environmental, a contractor for EQT, employed Hopkins.OSHA issued a serious citation that alleged Central Environmental had employees using headlamps that were not "intrinsically safe" to prevent sparks, fires or explosions.The citation included a proposed fine of $4,500. An official from Central Environmental did not immediately return a call seeking comment on the OSHA citation.OSHA lists violations as serious if "there is substantial probability that death or serious physical harm could result from a hazard about which the employer knew or should have known."Records indicate that officials could not conclusively determine the source of the ignition that led to the explosion.But OSHA said Central Environmental used improper headlamps "for illumination during hours of darkness when checking brine tank levels." Nearby residents said the explosion that killed Hopkins occurred about 6:45 p.m. DEP inspectors arrived onsite about 8:45 a.m., records show.OSHA also issued two "other than serious" citations that involved not having proper employee training on the use of fire extinguishers and having an electrical receptacle without a faceplate. Those carried no proposed penalties.EQT calls itself "a major player in the Appalachian Basin," with more than 3.5 million acres of drilling rights in Kentucky, Pennsylvania, Virginia and West Virginia.Parkersburg-based Central Environmental says it is "a leading provider of a comprehensive suite of environmental, transportation, energy and industrial services," including the management of gas industry wastewater."Between 2003 and 2011, the most recent figures available, at least 17 workers in West Virginia's oil and gas industry were killed on the job, according to an analysis by the U.S. Department of Labor's Bureau of Labor Statistics.Reach Ken Ward Jr. at email@example.com or 304-348-1702.