Nabors Industries Ltd. (NBR), the world’s largest onshore rig contractor, said hydraulic fracturing doesn’t pose a major risk to underground water supplies in response to questions from the U.S. Securities and Exchange Commission.

Publicly available fracking studies, including the Environmental Protection Agency’s 2004 report, haven’t “substantiated a material risk” of drilling fluids spilling into other areas, Hamilton, Bermuda-based Nabors said in a July 27 letter to the SEC made public in a filing today.

The SEC has reviewed filings and asked companies such as Nabors, Halliburton Co. (HAL) and SandRidge Energy Inc. (SD) to answer questions about fracking operations, a technique that blasts water, sand and chemicals into underground rock to unlock hydrocarbons. The SEC said possible risks to comment on include spillage and fracking fluids seeping underground.

Nabors told the SEC the biggest risk it faces related to fracking comes from the threat of increased regulations.

“Increased regulation of hydraulic fracturing could result in reductions or delays in drilling and completing new oil and natural-gas wells, which could adversely impact the demand for fracturing and other services,” the company said.

The SEC has completed its review of Nabor’s filings, the company said.

Nabors rose 1.2 percent to $14.12 at the close in New York.

To contact the reporter on this story: David Wethe in Houston at dwethe@bloomberg.net

To contact the editor responsible for this story: Susan Warren at susanwarren@bloomberg.net