BROOMFIELD, Colo. -

Researchers from NASA and other agencies are launching a month long study to identify sources of high summer ozone levels along Colorado's Front Range from Denver north to Fort Collins.

Scientists already have found that booming oil and gas fields there emit three times more methane and nearly eight times more cancer-causing benzene than previously thought. The aerial study that starts Tuesday will focus on the levels and sources of ozone

NASA will fly two planes to test the air at higher elevations while scientists will test the air below that with balloons.

State officials recently enacted rules to reduce emissions of the gases that contribute to ozone pollution, including infrared monitoring on leaks from oil and gas storage facilities.