A scientist for the National Oceanic and Atmospheric Administration discovered that the company that processes Colorado’s methane data was reporting erroneous measurements.

CPR reports that Gabrielle Petron realized that the reported measurements of methane at sites in Denver and Platteville were lower than those from the South Pole, which has some of the purest air on Earth.

Petron first alerted the state’s regulators in 2014, when a different company processed the methane data. However, two years later, the state switched vendors when Atmospheric Analysis and Consulting in California came in with the lowest bid.

It costs Colorado $84,000 per year to send canisters of methane to California every six days for testing.

The data problems appear to be correlated with routine maintenance of the lab’s equipment. But even after the state corrected its figures, there are some data points that still appear to be the result of erroneous processing.

“We’re not investing the massive amounts that NOAA might have available or some of the other research institutions to finely calibrate that level because that’s not our primary task. Our primary task is to reduce those emissions at the source,” said John Putnam, the head of Colorado’s environmental programs, according to CPR.

Methane is a potent greenhouse gas that has 84 times the warming potential of carbon dioxide in its first two decades after release. Nearly one-third of the country’s methane emissions stem from the oil and gas industry.