Three firefighters died on Saturday and two were burned in a blaze sweeping the Utah-Colorado border, the U.S. Wildland Fire Service said in a statement.

The crew was helping fight the Knowles and Gore wildfires, the statement said. Several agencies have deployed firefighters to western Colorado, where those fires merged with the Snyder fire and have devoured 28,000 acres.

Flames suddenly overwhelmed the federal firefighters, who tried to take shelter amid the heat and smoke, the Department of Interior said in a statement.

“The U.S. Wildland Fire Service stands united with the U.S.D.A. Forest Service in grief and in our unwavering support for the loved ones left behind,” the agency said in a statement. The agency did not identify the victims.

Wildfires over the past week have charred the Southwest, where warmer winters, low snowpack and high winds have turned the arid landscape into fuel. Fires have reached into Colorado, Arizona, New Mexico and Nevada.

Gov. Jared Polis of Colorado declared a disaster late Saturday in response to the out-of-control fires in the western part of that state. The move centralizes the response and activates the state’s National Guard.

In Utah, 11 large wildfires raged as of Sunday morning, blackening more than 208,000 acres. The largest is the Cottonwood fire, which started near the city of Beaver, in the southwestern part of the state.

That blaze has grown to at least 93,000 acres in a week, with none of it contained, according to the U.S. Forest Service. Gov. Spencer Cox called Cottonwood the “most destructive fire in the state’s history” in terms of property loss. No injuries or deaths have been reported.

Firefighters on the ground and in the air had to pull out on Friday, and scout for safer ways to attack the blaze, the U.S. Forest Service said.

“The conditions that we have on our fire are pretty persistent across the state,” said Alyssa Mason, a spokeswoman for Great Basin Team 5, the federal group leading the response, on Saturday.

Fires can start innocently, she added. A chain dragging behind a truck can set off sparks and ignite roadside brush. State authorities have taken precautions to limit the threat. Last week, Governor Cox signed an executive order temporarily restricting fireworks through the July 4 holiday weekend.

Red flag warnings remain in effect across the Southwest. Winds could reach up to 40 miles per hour and humidity is expected to remain low, according to the National Weather Service.

As smoke has billowed over the mountains and canyons, residents have watched their cabins and campgrounds, homes and infrastructure disappear in the flames.

Evacuation orders have been issued across Colorado. Communities outside the city of Ouray, in the southern part of the state, have been ordered to leave. Video on social media shows the surrounding ridgeline engulfed in flames, as the fire ominously rushes downhill.

“There are only so many places for attacking fire in steep terrain, and first responders have to be very diligent where they put people,” Ouray County said in a statement.

In Mesa County, Colo., on the border of Utah, authorities have issued a pre-evacuation order, as pop-up fires grow into each other, burning nearly 30,000 acres in the last 24 hours.

“It’s pretty somber here,” said Cody Davis, a county commissioner in Grand Junction, where the skies have been thick with smoke.