The Scottish Environment Protection Agency (Sepa) is launching an investigation into claims that methane is "bubbling up" in wells drilled to test for the gas in coal seams near Canonbie in Dumfries and Galloway. The claim is denied by the company that owns the wells.
The Sunday Herald received information claiming gas was escaping in the wells.
The information was passed to Sepa, which promised to investigate. "Sepa has recently become aware of information regarding the potential release of gas from coal-bed methane wells in the Canonbie area," said a Sepa spokesman. "Sepa will shortly be carrying out investigations into this."
The spokesman said once investigations were complete Sepa would consider whether follow-up work in line with its enforcement policy would be needed.
Methane, a major component of flammable natural gas, can be an explosion risk in some concentrations. It also causes 21 times more global warming than carbon dioxide.
"The allegation underlines legitimate concerns surrounding unconventional gas," said Labour's environment spokeswoman, Claire Baker MSP. "There is a desperate need for clarity, transparency and a truly robust scrutiny process to assess the safety of such sites before we start to see a rapid expansion of unconventional gas."
Eight exploration and pilot production wells were dug in the Canonbie area by Greenpark Energy in 2007 and 2008, and Sepa issued two licences permitting the controversial technology of fracking to extract underground gas.
Greenpark was taken over by Australian company Dart Energy in April 2012.
"We strongly deny that we have well integrity issues with any of our wells, nor is there danger of leaking of natural gas," said a spokesman for Dart Energy on Friday afternoon.
He added: "Sepa has confirmed within the past few hours that the only suggestion that wells are leaking has come from the Sunday Herald newspaper."