The heat has been turned up in the ongoing investigation into last year's Crandall Canyon Mine disaster in which two separate collapses claimed the lives of nine men.

The U.S. Department of Labor announced Wednesday that its Mine Safety and Health Administration has asked the U.S. attorney for Utah to conduct a criminal investigation of the Aug. 6, 2007, collapse at Crandall Canyon Mine near Huntington that killed six men.

An attorney for mine operator Genwal Resources called MSHA's referral more finger-pointing at a time when MSHA's own actions at Crandall Canyon are under scrutiny.

"Given the profound bias and factual leaps reflected in MSHA's own report, as highlighted by the Department of Labor's independent review, this development comes as no surprise," attorney Kevin Anderson said in a statement to the media.

Anderson accused MSHA of suppressing public access to information the agency is using to support its "sensational" claims.

"Through its investigation of the tragic accidents last year at Crandall Canyon, MSHA determined that the operator and its engineering consultants demonstrated reckless disregard for safety," MSHA acting assistant secretary of labor Richard Stickler said in a statement Wednesday. "MSHA has referred this case for possible criminal charges."

Anderson said Stickler's statement is "reckless, irresponsible and without factual basis."

"The facts demonstrate that Genwal Resources Inc. endeavored in good faith to follow safe mining practices and truly believed the mine was safe — a belief that was shared at the time by MSHA itself," Anderson added.

Utah U.S. Attorney Brett Tolman's office this year has been working with federal agents in looking into what happened Aug. 6, 2007, when a mine bounce that registered as a 3.9 magnitude earthquake trapped and killed six miners.

"There is an ongoing investigation, and that will continue," said U.S. Attorney spokeswoman Melodie Rydalch.

Previously, House Education and Labor Committee Chairman George Miller, D-Calif., called on the Justice Department to conduct an investigation into whether mine operators conspired to withhold information about bounces prior to the day of the collapse. Three more men died Aug. 16, 2007, during another bounce while trying to rescue their trapped colleagues.

Rydalch said this week's referral from MSHA and Miller's request are being taken "very seriously," and that Tolman's investigation will be "exhaustive."

In July, MSHA announced it was fining mine operator Genwal Resources Inc., owned by Murray Energy CEO Robert Murray, more than $1.3 million for "alleged violations that directly contributed to the deaths of six miners last year." MSHA also fined mining engineering consultants Agapito Associates Inc. $220,000 for "an allegedly faulty analysis of the mine's design."