The amount of methane being leaked from natural gas production sites has been hugely underestimated, according to a “bombshell” new study released on Tuesday.

In a paper published at Energy & Science Engineering, expert and gas industry consultant Touché Howard argues that a much-heralded 2013 study by the University of Texas relied on a faulty measurement instrument, the Bacharach Hi-Flow Sampler (BHFS), causing its findings to low-ball actual emission rates “by factors of three to five.”

“The data reported by the University of Texas study suggest their measurements exhibit this sensor failure, as shown by the paucity of high-emitting observations when the wellhead gas composition was less than 91% CH4, where sensor failures are most likely,” Howard writes, “during follow-up testing, the BHFS used in that study indeed exhibited sensor failure consistent with under-reporting of these high emitters.”

Jamie Henn, communications director for 350.org called Howard’s findings a “bombshell,” adding: “The more we learn about fracking, the worse it is for the environment.”

If Howard is correct, the study throws into question countless other estimates of methane emissions from natural gas production through hydraulic fracturing, or fracking, which has been hailed as a low-emission energy solution.