Story highlights The High Park Fire is 50% contained, authorities reported Monday evening

The fire has burned more than 58,000 acres, fire officials say

More than 1,700 firefighters are battling the flames

A man is arrested for posing as a firefighter

Firefighters in northern Colorado made progress battling a raging wildfire in the hills west of Fort Collins on Monday despite high temperatures, low relative humidity and gusty winds that whipped up the blaze.

The High Park Fire had consumed more than 58,700 acres of woodland by Monday evening, but it was about 50% contained Monday night, authorities reported. Residents of some homes on the east side of the fire were allowed to return home, but people from several other neighborhoods remained under mandatory evacuation orders.

More than 1,700 personnel were battling the blaze.

Michael Stillman Maher, 30, was not one of them, although he allegedly wanted people to think he was, officials said. A fire chief reported seeing the Denver man driving a truck with a stolen government license plate and carrying phony firefighter credentials in the fire area Sunday night, officials said.

Maher was arrested in a Fort Collins bar early Monday morning and charged with impersonating a firefighter and theft.

The 9-day-old fire has destroyed more than 180 homes, and that number is expected to grow. Firefighters are also concerned that the blaze could shift toward dense stands of trees that have been killed by beetle infestations, according to InciWeb, a U.S. multiagency fire response website.

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"It just feels really dire. It's scary," resident Lupe Sandoval told CNN affiliate KUSA TV . "You feel bad for everybody."

The National Weather Service rates the fire risk in six Western states on Monday as critical. Red flag warnings are posted across 10 states, noting high winds, low humidity and warm temperatures.

The blaze has moved through forests and neighborhoods, forcing thousands of evacuations and leaving a trail of destruction. It has claimed one life, a 62-year-old woman found dead in her burned home last week.

"It will be some time before this fire is out, but our challenge now is to make sure we do everything to contain the damage," said Agriculture Secretary Tom Vilsack, who oversees the Forest Service and toured the Colorado firefighting areas.

Colorado Gov. John Hickenlooper said a tree struck by lightning sparked the mammoth blaze.

Elsewhere in Colorado, firefighters are battling a fire near Pagosa Springs that broke out last month. That blaze, also blamed on lightning, had grown to more than 13,000 acres by Monday night and was 30% contained.

And a new fire broke out Sunday and quickly spread to 200 acres near Pueblo, forcing some evacuations of residents.

In New Mexico, the Whitewater Baldy Fire has scorched more than 296,000 acres, the agriculture secretary said.

More than 3,200 fire personnel from across the United States are helping local departments battle the fire, which began on May 16. The blaze was 80% contained as of Sunday.