Two years after a Utah mine collapsed, entombing six miners more than 2,000 feet under a mountain and also killing three members of a rescue team, the state's coal operators are backing away from rich coal reserves held deep under the ground.

Two years after a Utah mine collapsed, entombing six miners more than 2,000 feet under a mountain and also killing three members of a rescue team, the state's coal operators are backing away from rich coal reserves held deep under the ground.

Coal mines have come under intense scrutiny in every part of the country, with the Mine Safety and Health Administration tripling fines against all coal mines last year, to $152.7 million.

But in Utah, where easy access to coal was exhausted more than a decade ago, operators say they have been hit especially hard because of the extreme depths at which they dig for coal.

The Crandall Canyon collapse in 2007 shows what can go wrong. A bounce, a type of seismic jolt, imploded with the force of two million pounds of explosives at Crandall, said Michael McCarter, a professor of mining engineering at the University of Utah.

The tremor flattened a section of the mine roughly the size of 63 football fields, leaving six miners entombed 2,160 feet under mountain cover. Another cave-in 10 days later killed three members of a rescue team, including a federal mining inspector.

Federal regulators, stung by criticism following mine disasters from West Virginia to Utah, quickly clamped down.

"We'll never know if we make the right decision — we'll just know when we make the wrong decision," said Kevin Stricklin, coal-mining boss for the Mine Safety and Health Administration.

But with federal inspectors on site practically every day, executives for several Utah mines grumble that the inspectors are writing up citations mostly for small offenses — a pile of coal dust there, a spill of grease here.

Utah's largest coal operator, St. Louis-based Arch Coal Inc., turned away from a deep coal seam at the Dugout mine in central Utah, leaving behind 4 million tons of coal a year ago.

McCarter and other mining experts question whether regulation has gone too far.

Mining authorities ordered a new method of longwall mining that effectively cuts West Ridge's reserves in half, "and I'm not really sure anybody has proven it any safer," McCarter said.

Others agree the tighter regulations are a welcome change, because companies for years got a free pass.

"It was a rubber stamp," said Mike Dalpiaz, the mayor of Helper and a United Mine Workers of America vice president. "We had to spill blood before they started paying attention."