Drilling at several natural gas wells in southwestern Pennsylvania released methane into the atmosphere at rates that were 100 to 1,000 times higher than federal regulators had estimated, new research shows.

Using a plane equipped to measure greenhouse gas emissions, scientists found that drilling at seven wells in the Marcellus shale formation emitted 34 grams of methane per second, on average. The Environmental Protection Agency has estimated that such drilling releases between 0.04 grams and 0.30 grams.

The study, published Monday in the Proceedings of the National Academy of Sciences, adds to research suggesting that the EPA is seriously underestimating methane emissions from oil and gas operations. The agency may issue its analysis of emissions today, which will give outside experts a chance to assess how well regulators understand the problem.