Photo by gocarts via Flickr)

Millions of gallons of toxic chemicals used by oil and gas companies in techniques used to extract gas from rock have been injected into wells, a report from the Committee on Energy and Commerce finds.

The report by Congressional Democrats discovered that 14 oil and gas companies used 780 million gallons of hyrdaulic fracturing, or hydrofracking, products, which included hazardous chemicals like lead and benzene.

The report also found that some of the companies could not even identify all of the chemicals used in the extraction technique.

Hydrofracking, a controversial high-pressure drilling process, uses a mixture of sand, water and chemicals to reach shale deep underground. The extraction method along with other advances in technology has contributed to an increase in gas production.

"Hydraulic fracturing has opened access to vast domestic reserves of natural gas that could provide an important stepping stone to a clean energy future," said the report, which was written by Representatives Henry Waxman of California, Edward J. Markey of Massachusetts and Diana DeGette of Colorado. "Yet questions about the safety of hydraulic fracturing persist, which are compounded by the secrecy surrounding the chemicals used in hydraulic fracturing fluids."

Democrats, led by Rep. Waxman, initiated an investigation into the popular practice before Republicans took control of the House last November.

Here are some of the reports key findings:

• Oil and gas companies used more than 2,500 hydrofracking products between 2005 and 2009 that contained 750 chemicals.
• Twenty-nine chemicals used by companies between 2005 and 2009 were found to be either known or possible carcinogens, regulated under the Safe Drinking Water Act, or listed as a hazardous pollutant under the Clean Air Act.
• Methanol, an air pollutant and candidate for regulation under the Safe Drinking Water Act, was the most widely used chemical, appearing in 342 hyrdofracking mixtures.
• BTEX compounds (benzene, toluene, xylene, and ethylbenzene) were found in 60 of the fluids used between 2005 and 2009 with companies injecting 11.4 million gallons of fluids containing at least one BTEX compound. BTEX is regulated under the Safe Drinking Water Act and is listed as a hazard in the Clean Air Act. Benzene is a known human carcinogen.

Read the entire report here.