An investigative report that details the findings of a year-long probe into the Upper Big Branch mine explosion paints a picture of a rogue coal operation in which basic safety measures were routinely flouted and federal regulators did little more than issue citations and walk away.

The 122-page report to West Virginia Gov. Earl Ray Tomblin (D), written by a panel of independent safety experts, includes interviews with dozens of miners, an examination of the disaster site and a review of thousands of pages of internal and public documents.

The panel concluded that the April 2010 disaster that killed 29 miners in West Virginia was “man-made” and could have been prevented.

The investigation was led by J. Davitt McAteer, director of the federal Mine Safety and Health Administration under President Bill Clinton, and recommended 52 safety changes. Many of them call for an increased and mandated use of technology to measure, gauge and record safety conditions to reduce human error and short-circuit fraudulent behavior.

“We are long past the time where we can accept the loss of 29 miners,’’ McAteer said at a Thursday news briefing. “If we are going to have a mining industry, we have to reform ourselves.”

McAteer and his team placed much of the blame for the worst U.S. mining disaster in 40 years on his former agency.

“Despite MSHA’s considerable authority and resources, its collective knowledge and experience, the disaster at the Upper Big Branch mine is proof positive that the agency failed its duty as the watchdog for coal miners,” the report said.

One unidentified longtime MSHA official told McAteer’s group that managers for Massey Energy, the mine’s owner, fought safety citations so vociferously that it began to shape how federal inspectors viewed the mines and softened their enforcement approach. “Massey trains our inspectors better than we do,” the MSHA official is quoted as telling the investigators.

In response to the findings, MSHA Director Joseph A. Main emphasized that his agency has stepped up enforcement since the disaster but agreed with most of the conclusions. He asked Congress to help with some of the recommended changes that would require new legislation.

“We are playing a significant role in making mines safer. Yet there are mine operators that don’t get it,” Main said. “They operate differently when MSHA is not there, and they know MSHA cannot be there all the time. That’s why we have called on Congress to provide us with more tools to protect miners. We need to make sure that recalcitrant operators do get it.”

The agency’s own investigation into the disaster is ongoing.

In a prepared statement, Massey general counsel Shane Harvey disagreed with the report’s assertion that the methane monitors, which measure the concentration of the combustible gas in a mine, were not functioning at Upper Big Branch. Harvey also disagreed with the report’s conclusion that the explosion was fueled by highly combustible coal dust.

“We disagree with Davitt’s conclusion that this was an explosion fueled by coal dust,” the statement said. “Again, we believe that the explosion was caused by a massive inundation of methane-rich natural gas. Our experts feel confident that coal dust did not play an important role.”

Nine months after the disaster, Massey agreed in January to sell its mines and other assets to Maryland-based Alpha Natural Resources. The sales agreement is subject to a shareholder-approval vote, which is expected to take place next month.

Although the report was critical of the MSHA, the harshest criticism was directed at Massey Energy. The safety experts said the company has created a work culture that encourages “deviant” behavior that includes falsifying safety reports.

“The April 5, 2010 explosion was not something that happened out of the blue, an event that could not have been anticipated or prevented,” the report said in its conclusion. “It was, to the contrary, a completely predictable result for a company that ignored basic safety standards and put too much faith in its own mythology.”