SALT LAKE CITY (AP) — Almost all of the air pollution in a rural corner of Utah comes from oil and gas drilling and a coal-fired power plant, leading scientists to believe those emissions are responsible for producing dangerous levels of ozone, a gas that is the main ingredient in smog.

Officials trying to learn the root cause of ozone formation held a news conference Tuesday in Vernal, about 125 miles east of Salt Lake City, to discuss preliminary findings of an industry-sponsored study.