Miners died in pursuit of better life: Obama

President Barack Obama says 29 victims in the worst US mining disaster in a generation died in pursuit of a better life and he's promising safer working conditions underground.

Obama planned to speak at a memorial service on Sunday afternoon for the victims of the April 5 explosion at the mine in Montcoal, West Virginia, owned by Massey Energy Co.

Investigators have detected high levels of two potentially explosive gases inside the Upper Big Branch mine and say it could be a month before they can get inside to determine what caused the blast.

Obama has ordered a broad review of coal mines with poor safety records and urged federal officials to strengthen laws "so riddled with loopholes that they allow unsafe conditions to continue." In excerpts of Obama's remarks released by the White House early on Sunday while the president vacationed in North Carolina, he pledged changes to an industry that provides valuable jobs in once-thriving mine country and a needed source of energy.

"We cannot bring back the 29 men we lost. They are with the Lord now," Obama said. "Our task, here on Earth, is to save lives from being lost in another such tragedy. To do what must be done, individually and collectively, to assure safe conditions underground."

Federal regulators have identified highly explosive methane gas, coal dust or a mixture of the two as the likely cause of the blast, but the ignition source is unknown.

A preliminary report suggests the blast may have been caused by a preventable buildup of methane gas mixing with coal dust. The report from Labor Secretary Hilda Solis and mine safety officials also raised concerns about a major increase in safety violations at the mine.

The report said the rate of serious violations in 2009 that required mine workers to leave while immediate repairs were made was nearly 19 times the national rate.

"In short, this was a mine with a significant history of safety issues, a mine operated by a company with a history of violations, and a mine and company that (the Mine Safety and Health Administration) was watching closely," the report said.

While Obama conceded the government was partly at fault for the disaster, he laid most of the blame for the latest accident on the mine's owner. "Safety violators like Massey have still been able to find ways to put their bottom line before the safety of their workers _ filing endless appeals instead of paying fines and fixing safety problems," Obama said on April 15.

Massey Energy called Obama's remarks "regrettable" and defended its safety record.

Ahead of the memorial service, where West Virginia Gov. Joe Manchin and Vice President Joe Biden also planned to speak, Obama cited the sacrifices miners make in their efforts to build a better life for their families.

"All the hard work. All the hardship. All the time spent underground. It was all for their families," Obama said. "For a car in the driveway. For a roof overhead. For a chance to give their kids opportunities they never knew; and enjoy retirement with their wives. It was all in the hopes of something better. "These miners lived _ as they died _ in pursuit of the American dream."

In his remarks, Obama said letters had poured into the White House after the April 5 disaster.

"They ask me to keep our miners in my thoughts. Never forget, they say, miners keep America's lights on. Then, they make a simple plea: Don't let this happen again."

The nation's top mine safety official is expected to face tough questions on Tuesday at the Senate's first hearing on the explosion.