By Mike Saucier
PHOENIX (Reuters) - Firefighters struggled against strong winds on Thursday to halt the advance of Arizona wildfires that have charred more than 30 square miles (78 square km) of dry ponderosa forest, brush and grass, and a blaze in nearby Colorado swelled overnight.
More than 1,000 firefighters in the two states battled at least five major blazes from the ground while air tankers and helicopters dropped water and fire retardant. Another fire erupted in Minnesota, encroaching on the northern town of Ely.
The Sunflower Fire, the largest of the blazes in central and eastern Arizona, has burned nearly 20 square miles (52 square km) in the Tonto National Forest, about 40 miles north of Phoenix, fire officials said.
Fire crews have managed to carve containment lines around just 10 percent of its perimeter since it erupted over the weekend, fueled by grass, chaparral and pinyon pine. But the fire was expected to slow as it hits previously burned areas and scars from a previous blaze.
"Our major concern is the anticipated red-flag weather tomorrow, which is low humidity and high winds," said fire information officer Rick Hartigan of the Arizona Central West Zone Incident Management team.
The blazes were the first major wildfires in Arizona this year, after a record 2011 fire season in which nearly 2,000 blazes together swallowed more than 1,500 square miles (3,900 square km), according to the National Interagency Fire Center.
The fires left a translucent veil of gray-brown smoke over the northeast Phoenix valley, obscuring views of the burning highlands nearby.
The Gladiator Fire, which prompted the evacuation of about 350 residents of Crown King in central Arizona earlier in the week, destroyed another home on Wednesday, bringing to four the number of ruined buildings, U.S. Forest Service spokeswoman Debbie Maneely said.
The blaze was caused by a structure fire on private property, authorities said, and it had ripped through nearly 9 square miles in the Prescott National Forest.
Officials said the fight against the blaze, which was 5 percent contained, might be hampered due to expected high winds that could force the grounding of retardant-dropping tankers. Crews of 500 firefighters and other workers fought to stop it from reaching Crown King.
But they said winds from the southwest may also help in pushing the fire to the north, away from Crown King, according to the Forest Service.
The containment of the other two fires, Elwood and Bull Flat, were also challenged by high winds.
The 2-square-mile (5-square-km) Elwood fire was 5 percent contained and officials were hoping that dug-in fire lines would hold in the face of expected 40 mile per hour winds, fire prevention officer Wilfred Steele said.
In nearby Colorado, a stubborn blaze burning in the Roosevelt National Forest about 20 miles northwest of Fort Collins, quadrupled in size overnight to 5,100 acres (21 squake km), fire officials said.
High winds caused the so-called Hewlett Fire to grow "substantially" and efforts of the roughly 400 firefighters have been hampered by the erratic winds and the steep, rugged Colorado terrain, incident commander Todd Richardson said.
The fire ignited on Monday, and fire officials believe it was human-caused. No structures have been lost but residents in several subdivisions in the area have been warned to evacuate should winds drive flames in their direction.
In Minnesota, a wildfire sparked by a downed power line ballooned to 100 acres (.4 square km) within hours on Thursday and crept within a few hundred feet of Ely in northern Minnesota, forcing some residents from their homes for a few hours, officials said.
Crews battled the fire with four airplane tankers and two helicopters from the air and 10 engines and a half-dozen bulldozers on the ground as windy, dry conditions fed the blaze.
There were no reports of injuries or damage to structures, and the precautionary evacuation of part of the city was rescinded by Thursday evening, officials said.
Ely is known as the gateway to the Boundary Waters Canoe Area Wilderness in far northeastern Minnesota. A wildfire burned 100,000 acres (400 square km) in the region east of the city last Fall.
Last year's Wallow Fire, the largest blaze in Arizona's history, started in late May and torched about 840 square miles (2,200 square km) of prime forest land in Eastern Arizona. Two Arizona cousins, who had left a campfire unattended, pleaded guilty to starting that fire.
(Additional reporting by Keith Coffman in Denver; editing by Cynthia Johnston and Mohammad Zargham)