Genwal Resources, the Murray Energy company that operated the Crandall Canyon mine in Utah where six miners were killed in a 2007 wall collapse and three rescuers died in a second implosion, is pleading guilty to violating mine safety laws and will pay a $500,000 fine.

According to The Salt Lake Tribune, the agreement must be approved by U.S. District Judge David Sam and stipulates that no charges will be filed against any other individuals or companies.The newspaper reports that family members of the lost miners are dissatisfied that a four-year investigation resulted only in two misdemeanor charges, neither directly related to the mine collapse.

Rep. George Miller (D-Calif.), senior Democrat on the House Education and the Workforce Committee, which investigated the mine disaster, agrees.

Regrettably, Congress’ work remains unfinished in preventing such mining tragedies from occurring in the first place. This case is proof positive that weak criminal sanctions under the Mine Act leave many prosecutors with limited penalties to punish those who engage in willful violations. That’s why we must strengthen the law to deter future tragedies and to give prosecutors meaningful tools to hold all those responsible for putting miners in unnecessary danger accountable, no matter where they stand in the corporate chain of command.

Many expected more from this four-year investigation, including me, and with the U.S. Attorney’s findings, we must move forward with legislative changes. The health and safety of America’s miners must not be held up by predictable partisan battles. Miners and their families shouldn’t have to wait for another tragedy to occur. It’s well past time we get back to work.”

Read more here and see the charging document and Genwal’s response.