FLAGSTAFF, Ariz. >> A wildfire burning in rugged terrain in a northern Arizona canyon grew significantly because of fires intentionally set by crews to rob the blaze of its natural forest fuels, officials said Saturday.

Crews have mostly completed burnout operations on the key northern flank of the Slide Fire and are preparing to make similar protection efforts on the fire’s western end. The burnout operations conducted Friday night by fire crews contributed to the heavy smoke over Sedona and Flagstaff. 

“They are making progress. Having the humidity and cooler temperatures was certainly very helpful. But we are by no means done yet,” Coronado National Forest Service information officer Gerry Perry said. 

There’s a chance of thunderstorms Saturday in the area that could bring much-needed moisture. But if such a storm doesn’t produce any rain, its winds could fan the fire.

The size of the human-caused fire had reached 16 square miles by Saturday morning. It had grown nearly 5 square miles since the latest report on its size.

It’s burning around Oak Creek Canyon, a scenic recreation area along the highway between Sedona and Flagstaff that would normally be filed with tourists as Memorial Day approaches. Slide Rock State Park, one of the most-visited tourist spots in Arizona, has been closed.

The goals for fire managers are to protect the 300 structures threatened in Oak Creek Canyon, keep the fire from pushing into the communities of Forest Highlands and Kachina Village to the east, and minimize the potential for flooding.

The Coconino County Sheriff’s Office said in a statement Saturday that they expect to lift the warning on Monday for the 3,200 residents of those two communities. Mandatory evacuations will likely remain in place in Oak Creek Canyon from Slide Rock State Park to Sterling Springs Hatchery.

Perry said crews working Friday night also focused on building protection lines to handle a finger of fire that took off in west Oak Creek. There were no homes in the area, and crews have made solid progress in protecting that area, Perry said.

Crews cleared out brush and conducted burnout operations to protect a power line that supplies electricity to Flagstaff.

No homes have been destroyed. The fire is 5 percent contained.