PHOENIX (AP) -- Firefighters cleared brush and dug containment lines Thursday as they tried to box in a wildfire burning north through central Arizona, hoping to stop it from reaching four nearby communities and forests hit by tree-killing beetles.
The Cave Creek Complex fire has charred 172,788 acres and is the second-largest wildfire in the state's history. It was burning about 20 miles southwest of the mountain communities of Pine and Strawberry, 25 miles south of Camp Verde, and five miles east of Black Canyon City, a community of about 4,500 near Interstate 17.
''It's looking real good,'' said fire spokeswoman Emily Garber. ''Our big concern is protecting the east flank and Black Canyon City. We think we have enough lag time to do so.''
No evacuations were planned but the highway patrol said they may need to close I-17 periodically throughout the holiday weekend if conditions become too smoky. The fire was six miles from the interstate Thursday afternoon.
Almost 1,600 people were fighting the fire, which about 40 percent contained along the south. A smaller portion of the fire was burning to the north and was not at all contained.
Firefighters in some areas got a boost Thursday from lighter winds and higher humidity. Relative humidity was at 10 percent and winds from the southwest were only expected to get up 20 mph, according to the National Weather Service in Phoenix.
''Things are kind of smoothing out, and that'll help firefighters,'' said meteorologist Ryan Kittell. ''But it's still pretty hot and dry.''
Crews stationed between the fire's western flank and Black Canyon City dug lines to create a space clear of vegetation and were trying to push the fire south into an area already scorched by an earlier fire. Firefighters also helped residents clear brush from around their homes, in case fire lines don't hold.
Residents worried as the flames licked closer and smoke plumes drifted overhead.
''It's just so big,'' said Black Canyon City resident Harvey Sheren, who along with his wife took the day off in case evacuations became necessary.
Others were taking a more watch-and-wait approach.
''You might as well take it with a grain of salt, a sense of humor, and pray for the best,'' said Black Canyon City resident Scooter Grider, who wasn't worried the fire would get close enough to trigger evacuations there.
On the north and eastern flanks, firefighters worked to stop flames from jumping the Verde River to the east and from reaching the town of Camp Verde to the north. The fire was 25 miles from the mostly ranch town, which is home to about 10,000 residents.
Crews up north were creating fire lines using existing roads between Campe Verde and the fire and digging hand lines in more remote areas. Once the lines are established, crews will set fires to burn away vegetation in the wildfire's path, said Chris Papen, a spokesman for the northern zone of the fire.
''The conditions are too unsafe to put firefighters right up to the fire,'' he said.
Authorities were concerned that if it crossed the Verde River, it could push into a canyon and move into Pine and Strawberry, which are just three miles apart and combined have fewer than 5,000 year-round residents. Ponderosa pine forest surrounding the towns has also been hard hit by tree-killing beetles in recent years.
Meanwhile, a finger of the fire had reached into the Pine Mountain Wilderness and was feeding on pine and juniper.
''I wouldn't say it's a huge concern, we just have to change strategies,'' Papen said. ''The brush is a fast, flash fuel but the timber takes longer to suppress.''
The Cave Creek Complex fire began as two lightning-sparked fires on June 21 near Cave Creek and within days had forced the evacuations of some 250 homes northeast of Phoenix. Eleven homes and three storage sheds were destroyed in that area before the fire moved on.
The Department of Environmental Quality issue a smoke advisory in northern Maricopa and southern Yavapai Counties, warning people to avoid outdoor activities in the early morning hours when smoke is thickest.