Following a fatal accident Thursday at one of its drilling sites in Towanda Township, Chesapeake Energy Corp. has shut down operations at the site and is actively investigating the cause of the employee's death, a Chesapeake official said Friday.

OSHA on Friday said it has also launched an investigation into the death of the employee, 31-year-old Greg Allen Henry of Athens, Tenn.

An OSHA investigator went to the scene of the accident on Friday, said Fred Reschauer, assistant director of OSHA's regional office in Wilkes-Barre.

All work-related fatalities at work sites undergo an investigation by OSHA, Reschauer said.

State police and Bradford County Coroner Thomas Carman both say Henry's death was an accident.

Henry fell from a natural gas drilling rig which is owned by Nomac Drilling Inc., a subsidiary of Chesapeake Energy. Henry was employed by Nomac Drilling, said Carman and OSHA spokesman Leni Fortson.

Henry was apparently attempting to dislodge a handrail while the drilling unit was being moved to another drilling hole site on the drilling pad when the handrail gave way and in doing so, he slipped and fell approximately 20 feet, state police said.

Henry "obviously had severe head trauma," Carman said.

An autopsy on Henry will take place at Lehigh Valley Medical Center in Allentown Sunday morning to determine if Henry suffered any other injuries, the coroner said.

The accident occurred at 5:40 p.m. on Thursday, Carman said. Carman said he pronounced Henry dead at the scene at 6:39 p.m.

Carman said that Henry was not wearing a safety harness. Asked whether Chesapeake would normally require an employee to wear a safety harness in such a situation, Carman replied that he had "no comment."

Chesapeake notified OSHA immediately after Chesapeake became aware of the accident, Chesapeake spokesman Brian Grove said.

Chesapeake did not respond to a question e-mailed to the company, which asked whether Nomac employees are required to wear a safety harness when working on drilling rigs.

OSHA spokesman Fortson said that OSHA will not comment on the findings of its investigation until it is complete.

Under federal regulations, OSHA must complete the investigation within six months, Fortson said.

Reschauer would not predict how long the investigation would take, as the length of time depends on each case's circumstances.

According to OSHA's Web site, OSHA has investigated two other accidents involving Nomac Drilling Inc. and Nomac Drilling LLC in the past five years.

In one of the incidents, which occurred on Dec. 25, 2006, employees on Nomac Rig No. 5, who were engaged in the drilling of a gas well, "were exposed to struck-by hazards when the head-block and the drill string assembly, weighing approximately 186,000 pounds, fell to the floor during tripping operations," according to the OSHA Web site.

Nomac Drilling LLC was fined $4,500 by OSHA after the accident, which occurred in Allison, Texas, Fortson said.

A second accident, which occurred in Crowley, Texas, was investigated by OSHA beginning on June 15, 2008, Fortson said.

However, Nomac was apparently not cited by OSHA for any violations in connection with the Crowley, Texas accident, Fortson said.

The Web site shows the results of OSHA investigations that are completed or "closed." Fortson said.

OSHA investigations that are still under way would not show up on the Web site, she said. Investigations that are contested or under litigation might also not show up on the Web site, she said.

James Loewenstein can be reached at (570) 265-1633; or e-mail: