A university study that claimed fracking for gas deep beneath the Earth's surface did not cause water contamination was led by a US professor with financial ties to the gas industry, a watchdog group said Friday.

Lead author Charles "Chip" Groat, of the University of Texas, told reporters when the research on hydraulic fracturing was presented at a major science conference in Canada in February that the university had turned down all industry funds for the study.

However, an investigation by the Public Accountability Initiative (PAI) found that Groat himself has been on the board of the Houston-based Plains Exploration and Production Company for several years.

Groat was paid more than $400,000 in cash and stock by the company in 2011, and holds a near $1.6 million stake in the company's stock, it said.

$1.6 million stake...wow.