CHARLESTON, W.Va. -- An independent investigation of the disaster at Massey Energy's Upper Big Branch Mine will closely examine whether surface mine blasting played any role in increasing methane concentrations underground prior to the deadly April 5 explosion, officials say.

Davitt McAteer, who was appointed as special investigator by Gov. Joe Manchin, said his team plans to look at where and when blasting occurred at the huge mountaintop-removal mines in the vicinity of the Upper Big Branch operation.

"Our examination will look not only specifically at the issue of whether there was a blast, but also at the overall question of where there is surface mine blasting in the general area, what are the consequences of that," McAteer said this week.

McAteer said he would review what, if any, impact other underground mining that took place above the Upper Big Branch tunnels might have had on methane being released into the area where the explosion occurred.

Surface blasting and nearby underground mining can make underground geology less stable, McAteer said, and increase the levels of methane being naturally released during the mining process.

Twenty-nine miners died in the April 5 explosion at Upper Big Branch, making it the worst U.S. coal-mining disaster in 40 years.

Mine safety experts believe the blast involved an ignition of methane gas that was made far more powerful by a buildup of explosive coal dust deep inside the mine. Upper Big Branch had been repeatedly cited for ventilation violations and accumulations of coal dust.

Funeral services were scheduled to continue over the weekend for some of the miners killed, even as investigators continue to try to fix the mine's damaged ventilation system so they can get underground to begin gathering evidence.

The Obama administration has harshly criticized Massey's safety record and promised to beef up mine safety protections, but the U.S. Mine Safety and Health Administration has not yet announced any plans to improve the transparency of its investigation process, which is usually shrouded in secrecy until a final report is issued.

Labor Secretary Hilda Solis did announce late Friday afternoon that the MSHA would conduct an "internal review" of its enforcement at Upper Big Branch prior to the disaster. Solis also said she had asked the National Institute for Occupational Safety and Health to identify a team of experts to "provide an independent analysis of MSHA's internal review.

"I am confident that MSHA will conduct a thorough and complete review of the actions of the mine operator and its own actions at the Upper Big Branch Mine," Solis said. "To ensure accountability, I've asked for an outside team to review the policy, process and substance of MSHA's internal review.

"This independent evaluation will help ensure that we're doing everything we can to protect the health and safety of America's miners," Solis said.

Davitt McAteer, who was appointed as special investigator by Gov. Joe Manchin, said his team plans to look at where and when blasting occurred at the huge mountaintop-removal mines in the vicinity of the Upper Big Branch operation.

"Our examination will look not only specifically at the issue of whether there was a blast, but also at the overall question of where there is surface mine blasting in the general area, what are the consequences of that," McAteer said this week.

McAteer said he would review what, if any, impact other underground mining that took place above the Upper Big Branch tunnels might have had on methane being released into the area where the explosion occurred.

Surface blasting and nearby underground mining can make underground geology less stable, McAteer said, and increase the levels of methane being naturally released during the mining process.

Twenty-nine miners died in the April 5 explosion at Upper Big Branch, making it the worst U.S. coal-mining disaster in 40 years.

Mine safety experts believe the blast involved an ignition of methane gas that was made far more powerful by a buildup of explosive coal dust deep inside the mine. Upper Big Branch had been repeatedly cited for ventilation violations and accumulations of coal dust.

Funeral services were scheduled to continue over the weekend for some of the miners killed, even as investigators continue to try to fix the mine's damaged ventilation system so they can get underground to begin gathering evidence.

The Obama administration has harshly criticized Massey's safety record and promised to beef up mine safety protections, but the U.S. Mine Safety and Health Administration has not yet announced any plans to improve the transparency of its investigation process, which is usually shrouded in secrecy until a final report is issued.

Labor Secretary Hilda Solis did announce late Friday afternoon that the MSHA would conduct an "internal review" of its enforcement at Upper Big Branch prior to the disaster. Solis also said she had asked the National Institute for Occupational Safety and Health to identify a team of experts to "provide an independent analysis of MSHA's internal review.

"I am confident that MSHA will conduct a thorough and complete review of the actions of the mine operator and its own actions at the Upper Big Branch Mine," Solis said. "To ensure accountability, I've asked for an outside team to review the policy, process and substance of MSHA's internal review.

"This independent evaluation will help ensure that we're doing everything we can to protect the health and safety of America's miners," Solis said.

Congressional leaders have promised hearings, and the state Office of Miners Health, Safety and Training will do a separate investigation that will coordinate with McAteer's team.

Across West Virginia on Friday, mine operators were observing a day with no underground coal production. Manchin requested the move to honor the fallen miners and to refocus workers and management on safety issues.

Also Friday, Massey published full-page newspaper ads that said the company "will do whatever is needed to attend to the needs of those who have lost loved ones in this horrific incident. This is our solemn duty, and we will meet it with a clear sense of responsibility."

The ads, headlined "An open letter to the citizens of West Virginia," also said, "Massey's members know the facts: that our mines exceed legal safety standards, that we fix safety hazards as soon as we find them, that we use the best technologies available to prevent accidents ... and that we have received national recognition and awards for safety precautions."

A day earlier, the family of miner William I. Griffith filed the first wrongful death case against Massey and its Performance Coal subsidiary stemming from the disaster. The suit was filed Thursday in Raleigh Circuit Court, and more suits are expected to follow.

Griffith and his wife, Melanie, were to celebrate their 33rd wedding anniversary on April 30. Griffith, 54, had worked for Performance Coal since 1992 and went into the mines in 1974, shortly after he graduated from high school.

Rachel Moreland, one of Griffith's lawyers, said Friday that he had been worried about safety conditions in the mine.

"He told his wife that if anything ever happened to him to get a lawyer," Moreland said.

Department of Environmental Protection officials said this week that they had not yet been contacted by the MSHA or the state mine safety office of McAteer concerning questions about surface mine blasting near the Upper Big Branch Mine.

DEP spokeswoman Kathy Cosco said that there are at least four surface coal mines in the vicinity of Upper Big Branch, with most of them being located to the south of the active mining area underground. All are Massey operations.

"The company is gathering the blast logs for the day of the explosion and is getting them to us," Cosco said. "Once we have them, we can determine the exact times and locations of shots that took place that day."

McAteer said, "We should be addressing the issues coming from the environmental side, and from the safety side.