congressional investigators in the US have discovered that oil and gas firms infused diesel fuel into onshore wells in several states over a four year period.
Tens of millions of gallons of diesel which seeped into the soil between 2005 and 2009 allegedly breached the Safe Water Drinking Act.
The Environmental Protection Agency said the diesel fuel was used by drillers as part of a process known as hydraulic fracking in which a water, diesel fuel and sand was injected into rock formations deep underground under high pressure.
According to the EPA the process opened up vast new deposits of natural gas to drilling through the opening of rock fissures to release oil and gas.
It is believed no state or federal regulators had issued permits for diesel fuel use in the hydraulic fracking.