A fourth firefighter died after he and several colleagues last month were overcome by a fast-moving wildfire near the Colorado-Utah border, authorities said Saturday.

Nathan Matthews, 43, of Lincoln, Nebraska, died Friday, the federal Interior Department said in a statement.

Matthews was assigned to the Rifle Helitack crew — a group that gets dropped by helicopter into remote areas to try to squelch new, rapidly expanding fires — and was one of five firefighters involved in a burnover who deployed tentlike emergency shelters to try to shield themselves when flames closed in on June 27. Three of them died at the scene: Emily Barker, 38; Nick Hutcherson, 27; and Sydney Watson, 26.

"This is another heartbreaking loss for our wildland fire family," said U.S. Wildland Fire Service Chief Brian Fennessy. "We mourn the loss of Nate while continuing to grieve the deaths of Emily, Nick and Sydney. Our hearts are with their families, friends, crewmates and everyone impacted by this tragedy. We remain committed to supporting those affected and honoring the legacy of all four firefighters who made the ultimate sacrifice in service to our nation."

A serious accident investigation team continues to review the circumstances surrounding the incident. 

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The Interior Department declined Saturday to discuss the surviving firefighter's current condition. Watson, Hutcherson and Barker were honored at a memorial service earlier this month. Memorial arrangements for Matthews weren't yet announced.

Wildfires continue to rage across the West

Meanwhile, several fierce wildfires in a summer of big ones continued burning across the western U.S.

One of the worst — and the one deemed top priority for firefighting efforts — was just a few miles north of Sisters, a central Oregon city of about 3,000 people.

Winds gusting up to 30 mph threatened to push flames into new areas. Firefighters made progress keeping the fire in check, however, and officials were optimistic the city would be in the clear once the worst of the wind died down Sunday.

“It's going to take a while to put it out entirely. But as long as it stops moving, I think that’ll get people to relax a little bit,” Sisters Mayor Jennifer Letz said.

As of Sunday, the lightning-caused fire had burned about 42 square miles and was 6% contained. About 30 people evacuated from areas north of Sisters were in a shelter at the local high school, with about as many more staying in recreational vehicles parked outside, Letz said.

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The city wasn't in any immediate danger, and business was carrying on like usual, Letz said.

“We’re not necessarily asking everybody to come to Sisters. But it’s safe here,” said Letz.

Months of dry weather, a record lack of snow in some areas, hot spells and erratic winds have contributed to the blazes in Oregon, Washington, California, Colorado and elsewhere this summer. In Canada, 926 fires were burning Saturday, including 82 deemed out of control, according to the Canadian Wildland Fire Information System.

About 300 aircraft and 5,300 people were involved in fighting the fires. They included 133 in northwestern Ontario alone, according to the province's Aviation, Forest Fire and Emergency Services agency.

The biggest in Ontario had covered some 1,200 square miles.

The Associated Press contributed to this report.