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A Heavy Type-1 Skycrane Helictoper dumps 2,000 gallons of water on the Slide Fire as it burns up Oak Creek Canyon on Friday, May 23, 2014, near Flagstaff, Ariz. The fire has burned approximately 7,500 acres. (AP Photo/Ross D. Franklin)

FLAGSTAFF, Ariz. (AP) — 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.

A Heavy Type-1 Skycrane Helictoper flies over the Slide Fire, above the route 89 A, before dumping a 2,000 gallon load of water as it burns up Oak Creek
A Heavy Type-1 Skycrane Helictoper flies over the Slide Fire, above the route 89 A, before dumping a 2,000 gallon load of water as it burns up Oak Creek Canyon on Friday, May 23, 2014, near Flagstaff, Ariz. The fire has burned approximately 7,500 acres and is five percent contained. (AP Photo/Ross D. Franklin) (Ross D. Franklin/AP)

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.

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.

A Heavy Type-1 Vertol Helictoper dumps 2,800 gallons of water onto the Slide Fire as it burns up Oak Creek Canyon on Friday, May 23, 2014, near Flagstaff,
A Heavy Type-1 Vertol Helictoper dumps 2,800 gallons of water onto the Slide Fire as it burns up Oak Creek Canyon on Friday, May 23, 2014, near Flagstaff, Ariz. The fire has burned approximately 7,500 acres and is five percent contained. (AP Photo/Ross D. Franklin) (Ross D. Franklin/AP)

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

Evacuations remain in place for a 2-mile stretch north of Slide Rock. The fire was 3 to 3 ½ miles away from the residential areas of Forest Highlands and Kachina Village, where 3,200 residents remained under pre-evacuation warnings.

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


Bill Morse, the public information officer for the Southwest Area Type 1 Incident Management Team, watches the Slide Fire as it burns up Oak Creek Canyon
Bill Morse, the public information officer for the Southwest Area Type 1 Incident Management Team, watches the Slide Fire as it burns up Oak Creek Canyon on Friday, May 23, 2014, near Flagstaff, Ariz. The fire has burned approximately 7,500 acres and is five percent contained. (AP Photo/Ross D. Franklin) (Ross D. Franklin/AP)


Smoke plumes from several spots along the Slide Fire heads skyward as the fire burns up Oak Creek Canyon on Friday, May 23, 2014, near Flagstaff, Ariz.
Smoke plumes from several spots along the Slide Fire heads skyward as the fire burns up Oak Creek Canyon on Friday, May 23, 2014, near Flagstaff, Ariz. The fire has burned approximately 7,500 acres and is five percent contained. (AP Photo/Ross D. Franklin) (Ross D. Franklin/AP)