FLEMINGTON, W.Va. -- A worker was killed Friday in an explosion at an EQT Corp. natural gas production site in Taylor County, officials said.

Cpl. C. Willis, a Harrison County 911 dispatcher, said an EQT employee originally reported an explosion at a well site near Flemington after finding a water truck driver at the site dead from apparent head trauma.

Kathy Cosco, a spokeswoman for the state Department of Environmental Protection, said the incident at an EQT natural gas well pad appeared to have occurred while an employee was attempting to transfer briny wastewater from an on-site tank to a truck.

"We are told it was a flash explosion that killed the employee, destroyed the tank and damaged the truck nearby," Cosco said. "Initial reports are that the tank contained brine and that the material in the tank spilled and there is likely hydraulic fluid from the truck on the ground, too."

Cosco said the source of the ignition was not immediately clear.

Mary K. Singleton, who lives about a mile away, said her house shook at 6:45 a.m.

"I heard an explosion, but didn't know what it was," Singleton said. "You never know around here.

"I got up and made sure the house was all right, but couldn't see anything," she said. "I didn't know what's going on. I asked my husband, 'You suppose it was a meteor?'"

The Flemington Volunteer Fire Department, Taylor County Sheriff's Department and Taylor County emergency crews were dispatched. Willis said the body of the victim was taken to Grafton City Hospital.

A spokeswoman for the U.S. Occupational Safety and Health Administration said her agency learned about the incident from the news media, and was launching an investigation.

EQT spokeswoman Linda Robertson said that the company's initial findings indicate the victim, a contractor for the company, was at the site to check fluid levels on water storage tanks.

"The safety and security of EQT employees and contractors is a core value and it's a sad day when we lose anyone within our community," Robertson said in a prepared statement. "Our sympathies go out to the families and friends of the deceased."

Pittsburgh-based EQT is one of the largest exploration and production companies in the Appalachian shale-gas field, with drilling rights to more than 3.5 million acres in West Virginia, Pennsylvania, Kentucky and Virginia.

Drillers inject massive volumes of water, sand and chemicals to hydraulically fracture, or frack, the rock in which gas deposits are trapped. The gas then flows up for collection, as does the brine. The DEP says some of the chemicals in the brine could be flammable.

Worker safety is among the growing concerns in northern and north-central West Virginia as a boom in natural gas production continues in the state's Marcellus Shale gas fields.

In June 2010, seven workers were hurt outside of Moundsville when a crew drilling a natural gas well hit a pocket of methane in an abandoned coal mine. And in August 2012, three workers were injured in an explosion at a drilling operation in Harrison County.

DEP said there have been five fatal accidents since 2008. Three have involved well sites, while two involved access road activities.