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Grayish-brown smoke from a large wildfire blamed for killing a woman in her home blanketed the foothills of northern Colorado on Tuesday.

The 68-square-mile Colorado wildfire has damaged more than 100 structures and forced hundreds of people from their homes. However, firefighters there and at a 56-square-mile fire burning in southern New Mexico have begun to make some progress digging line around the blazes.

In Colorado, a smoky haze stretched early in the day from near the Wyoming border to the Denver area, signaling good news for firefighters. The smoke was trapped by cool air and calm skies, National Weather Service meteorologist Frank Cooper said. Strong winds that helped spread blaze in Colorado and New Mexico over the weekend carried smoke as far away as Kansas and Nebraska at the time.

Visibility was reduced to just about a mile near Longmont, Colo., in the morning and the state health department warned that air is unhealthy to breathe in such conditions.

The haze began to dissipate as the weather got warmer but forecasters say it could possibly return Wednesday morning.

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    The New Mexico fire, near the mountain community of Ruidoso, is now 30 percent contained after firefighters in took advantage of a break in hot, windy weather to build lines on Monday.

    The Colorado fire, fire burning 15 miles west of Fort Collins, was 5 percent and firefighters were hoping to double that progress Tuesday.

    Authorities there plan to allow 90 residents back to their homes but others elsewhere were being warned to be ready to leave.

    The massive wildfires in the drought-parched states have tested the resources of state and federal crews.

    Wyoming diverted personnel and aircraft from two fires there to help with the Colorado fire, and Canada lent two aerial bombers following the recent crash of a U.S. tanker in Utah. An elite federal firefighting crew also arrived to try to begin containing a fire that destroyed at least 118 structures.

    The U.S. Forest Service said late Monday it would add more aircraft to its aerial firefighting fleet, contracting one air tanker from Alaska and four from Canada. Two more air tankers were being activated in California.

    The announcement came after Colorado's U.S. House delegation demanded that the agency deploy more resources to the fire.

    Authorities confirmed Monday that one person died in the Colorado fire.

    The family of Linda Steadman, 62, had reported her missing after the fire started Saturday, sheriff's officials said. Her home received two evacuation notices that appeared to go to her answering machine, and a firefighter who tried to get past a locked gate to her home to warn her was chased out by flames that he later saw engulf her home, Sheriff Justin Smith said.

    Investigators found remains in her burned home Monday that haven't been positively identified yet, but her family issued a statement saying Steadman died in the cabin she loved, Smith said.

    In a letter to the Forest Service, Colorado's congressional delegation said the need for firefighting aircraft was "dire." U.S. Sen. Mark Udall urged President Barack Obama to sign legislation that would allow the Forest Service to contract at least seven large air tankers to add to its fleet of 13 — which includes the two on loan from Canada.

    The temporary additions to the firefighting aircraft fleet will make 17 air tankers available to the forest service, which has deployed 10 air tankers, 62 helicopters and 4,000 personnel to more than 100 fires nationwide.

    One of the region's most potent aerial firefighting forces — two Wyoming Air National Guard C-130s fitted to drop slurry — sat on a runway in Cheyenne, 50 miles north of the Colorado fire. The reason: The Forest Service, by law, cannot call for military resources until it deems that its fleet is fully busy. It also takes 36 hours to mobilize the crews and planes, officials said.

    "They just haven't thrown the switch yet because they feel like there are adequate resources available," said Mike Ferris of the National Interagency Fire Center in Boise, Idaho.

    Evacuees in Colorado expressed gratitude for the help.

    "They're doing the best they can," said Barb Hermsen as she watched a helicopter make daring raids through smoke and flame to protect homes. "We know how much they have to go through, and where they're going — man, it's crazy."

    Unable to return home, evacuee Cy Johnson set up a stand in the back of a pickup truck to hand out water and sandwiches to fire crews. "You're doing something. At least you're doing something," he said.

    An estimated 35 structures have been damaged or destroyed by the blaze near Ruidoso, and fire managers expect that number to grow once damage assessments are done. Hundreds of people have also been forced to flee.

    Elsewhere in New Mexico, firefighters made slow progress against the largest wildfire in state history. The blaze has charred 435 square miles of forest since it was sparked by lightning in mid-May, and was 37 percent contained Monday.

    Arizona's state forestry division dispatched two water tenders and 15 fire trucks to New Mexico, which also welcomed the arrival of a DC-10 jet that can lay a 100-yard-wide, mile-long line of retardant or water.

    Fire bosses in New Mexico and Arizona ordered more elite crews, engines and air support from the Southwest Coordination Center in Albuquerque, where director Kenan Jaycox said resources are approaching full capacity.

    "It's a balancing game," Jaycox said.

    At least 18 large wildfires are burning in nine U.S. states. The National Interagency Fire Center said 4,000 of 15,000 federal firefighters are deployed at fires around the country.

    Forest Service Chief Tom Tidwell has long insisted the federal government has enough resources to respond to a year-round wildfire season driven by drought, heat, decades of fighting forest fires rather than letting them run their natural course, and bark beetle-killed trees.

    He said the agency has the authority to transfer funds from other accounts to meet firefighting costs.

    Some 1,459 square miles have burned across the country this year — less than the same period in 2011, when 6,327 square miles burned.

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    Associated Press writers Susan Montoya Bryan in Albuquerque, N.M.; Felicia Fonseca in Flagstaff, Ariz.; and Mead Gruver in Cheyenne, Wyo., contributed to this report.