( CNN ) -- The U.S. government Thursday announced its highest penalty for coal mine safety violations , $ 1.85 million , for a collapse that killed six miners in Utah last year . Supervisory Mining Engineer Joe Zelanko on Thursday describes the earth movements at Crandall Canyon mine . Insufficient pillar support and activity in areas that should not have been mined caused the August Crandall Canyon mine collapse , federal investigators found . The government fined the mine operator , Genwal Resources , $ 1.34 million `` for violations that directly contributed to the deaths of six miners last year , '' plus nearly $ 300,000 for other violations . The government also levied a $ 220,000 fine against a mining consultant , Agapito Associates , `` for faulty analysis of the mine 's design . '' The mine 's owner had insisted that earth movement detected at the time of the collapse had caused the disaster . But investigators found instead that the collapse caused the earth movement . `` It was not -- and I repeat , it was not -- a natural occurring earthquake , '' said the government 's top mine safety official , Richard E. Stickler . Stickler , the acting assistant secretary of labor for mine safety and health , said , `` pillars failed under excessive load and ejected coal very violently . '' Stickler also said the mine 's operator `` was taking more coal than allowed from the barrier pillars and the floor . '' `` This dangerously weakened the strength of the roof support , '' Stickler said . In addition to the six miners killed in the initial cave-in August 6 in northwest Emery County , three would-be rescuers died 10 days later in a subsequent collapse . The bodies of the six miners killed in the initial collapse were never recovered . Richard Gates , the lead investigator for the government , said the pillars in the mine `` simply were not large enough to support the load . '' That resulted in a `` catastrophic failure of pillars over a broad area , '' as large as half a mile , he said . University of Utah scientists said in June that the collapse was not the result of an earthquake . `` As seismologists , we 're as certain as we can be that the seismic event registered as a magnitude-3.9 shock was due to the collapse of the mine and not a naturally occurring earthquake , '' said Walter Arabasz , director of the university 's Utah Seismograph Stations , in a written statement . Earlier this year , a Labor Department report criticized Mine Safety and Health Administration officials for approving plans for a risky mining technique , known as retreat mining , that was in use before the collapse . In the process , miners remove pillars of coal that support the roof of a chamber one by one , allowing the roof to collapse behind them . Mine owner Bob Murray repeatedly denied in the days after the disaster that his company practiced retreat mining at Crandall Canyon . He later admitted that the practice had been used at the mine but said it was not being done at the time of the disaster .
Feds : Violations by Utah mine 's operator led to 2007 collapse that killed six . Bad design , improper mining led to Crandall Canyon collapse , feds say . Mine operator fined more than $ 1.5 million .