LAS VEGAS - Fire crews burned forest undergrowth Tuesday near homes in the mountains northwest of Las Vegas to protect them from one of two large Nevada wildfires while local casino owners offered rooms to evacuees.

The wildfire burning northwest of Las Vegas was within a quarter-mile of homes and has charred an area nearly the size of Manhattan, authorities said. Billowing smoke were visible Tuesday from downtown and fine ash fell nearby.

In northern Nevada, more than 1,060 firefighters worked to stem the spread of a bigger but more remote wildfire that grew Monday to 40 square miles in the Pine Nut Mountains southwest of Reno.

Lyon County sheriff's deputies went door-to-door to ask people to evacuate Pipeline Canyon.

No homes have been lost in either fire, but fire officials said containment may not come on either fire until next week.

Fires were also burning across the West in California - where 100 mountain cabins were destroyed and 120 homes remained threatened in San Diego County - and in Alaska, Idaho and Arizona.

In Arizona, a memorial service was held Tuesday in Prescott for 19 members of a Hotshot crew killed June 30 while fighting a wildfire near Yarnell north of Phoenix. Speakers included the lone surviving crew member and Vice President Joe Biden.

In southern Nevada, no homes have been damaged and none of 800 firefighters has been injured battling the 31-square-mile Carpenter 1 fire on Mount Charleston, U.S. Forest Service spokesman Jay Nichols said. Officials said the fire was about 15 percent contained.

One portion of the blaze "bumped" the edge of state Route 157, threatening to cut off the main highway in and out of the evacuated Kyle Canyon area some 25 miles outside Las Vegas. No homes were nearby, Nichols said.

Smoke billowing from the lightning-sparked blaze was visible for an eighth day from Las Vegas.

The Clark County Department of Air Quality issued a health advisory that officials said would remain in effect through Sunday.

In northern Nevada, the 25,700-acre Bison Fire straddled the Douglas and Lyon county lines near Gardnerville and Carson City. It doubled in size Monday, but stabilized Tuesday after charring an area about two-thirds the size of Washington, D.C. Containment was reported at 25 percent.

One of 720 firefighters suffered a knee injury as crews battled gusty winds, low humidity and temperatures in the 90s, fire spokeswoman Lisa Ross said.

Douglas County commissioners declared a state of emergency to enable the county to seek more state and federal assistance.

Ross put the cost of battling the fire since it was sparked by lightning July 4 at about $3.5 million.

The Federal Emergency Management Agency has promised to reimburse Nevada for 75 percent of the cost of fire suppression on the nearly 20,000-acre Carpenter 1 fire near Las Vegas.

Federal Bureau of Land Management spokeswoman Hillerie Patton said Tuesday that the cost was approaching $5 million.

Officials say more than 500 residents have been unable to return to homes in Trout, Kyle, Lee, Harris Springs and Lovell canyons since the weekend. Another 98 teenagers remain evacuated from a Clark County youth correctional camp.

Several local casino companies teamed with the American Red Cross of Southern Nevada to provide hotel rooms to evacuees, and the Nevada Restaurant Association worked with the Red Cross to provide meals for firefighters working to protect about 400 mountain homes.

Cannery Casino Resorts executive Xavier Walsh said his company was willing to provide up to 40 rooms for the 10 days that fire managers say families may be displaced.

In other wildfires burning in the West:

- In Arizona, residents were allowed to return Tuesday to about 100 of the 200 homes evacuated due to a wildfire in Kearny, located 73 miles southeast of Phoenix. The fire burned has burned about 300 acres of dense vegetation and one house since Monday. It was 5 percent contained.

-In Northern California, more than 800 firefighters battled a 160-acre blaze near Kyburz, west of South Lake Tahoe. The El Dorado National Forest wildfire hadn't damaged any homes or required evacuations. Containment was about 40 percent Tuesday.

- In Southern California, a wildfire burned more than 100 cabins at a Shriner's International mountain camp near Julian, 60 miles east of San Diego in the Cleveland National Forest. The 7.3-square-mile fire was 15 percent contained, but threatens evacuated campgrounds and about 120 homes, mostly vacation cabins, officials said Tuesday.

-In southern Colorado, the East Peak Fire was declared 100 percent contained Tuesday. The lightning-sparked fire burned 13 homes.