Rep. Henry Waxman of California, the ranking Democrat on the House Energy and Commerce Committee, Edward J. Markey, D-Mass. and Diana DeGette, D-Colo., have been investigating the use of toxic substances, including diesel fuel, in the fluids injected into natural gas wells in the hydraulic fracturing process meant to liberate gas by creating fissures in rock, usually shale, to allow it to be extracted.
Twelve companies employing fracking in Texas, Oklahoma, Louisiana, Colorado, Wyoming, North Dakota, West Virginia and Pennsylvania said they used 32 million gallons of diesel fuel as a fracking fluid ingredient from 2005 to 2009.
Oil companies have maintained that fracking does not affect drinking water, despite reports of methane and other chemicals in residential wells near fracking activities.
In a letter to the Environmental Protection Agency, Waxman, Markey and DeGette said the amount of diesel actually used was under-reported by almost 500,000 gallons, the Los Angeles Times reported Tuesday.
They pressed the agency for better oversight and more uniform reporting requirements.
Notable deaths of 2014 [PHOTOS]