YOSEMITE NATIONAL PARK (AP) — A fierce wildfire that scorched part of Yosemite National Park burned less intensely in places that had fires in recent years — a finding that researchers said Wednesday supports a belief that controlled burning often curtails extreme fires.

The U.S. Forest Service study focused on areas of the Rim Fire that burned 400 square miles in Stanislaus National Forest, Yosemite’s backcountry and private timber land.

It was the largest fire in the recorded history of the Sierra Nevada. It destroyed 11 homes and cost more than $125 million to fight.

Areas hit by the Rim Fire within Yosemite had burned within 14 years and experienced less intense flames, said U.S. Forest Service Pacific Southwest Research Station, which authored the study.

The study also said wildfires are almost impossible to contain after they turn into a storm of smoke, gas and ash that race across treetops.

“The specific conditions leading to large plume formations are unknown,” said Jamie Lydersen, lead author of the study. “But what is clear from many observations is that these plumes are associated with extreme burning conditions.”

Studies into the makeup of Yosemite’s forest done three years before the Rim Fire provided a point of comparison, researchers said.

Researchers recommend that forestry agencies with shared borders and interests combine their efforts to conduct controlled burns during moderate weather conditions, giving them the best chance for to avoid massive high-intensity fires.

Bow hunter Keith Matthew Emerald, 32, has pleaded not guilty to a four-count indictment charging him with starting an illegal fire and lying to federal agents. Authorities said he lost control of a campfire on Aug. 17, 2013.