DURANGO, Colo. -- Hard work at high elevations is taking its toll on firefighters battling a 70,975-acre blaze in southwestern Colorado.

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Several firefighters have been sent home after suffering from altitude sickness, said incident medical specialist Marla Nichols.

"We are losing 2 to 3 percent of line people to this," Nichols said.

Altitude sickness typically occurs at 6,500 feet above sea level or higher. Durango and the fire camp sit at 6,512 feet, and some firefighters have been working at elevations as high as 11,000 feet.

"Since June 11, I've seen at least 50 people with it," Nichols said.

One firefighter suspected to be suffering a heart attack was rushed to a hospital with what turned out to be high altitude pulmonary edema, a severe form of altitude sickness that causes a person's lungs to fill with liquid. He was sent home to Georgia, Nichols said.

Nichols said new crews arriving at the scene are sent immediately to the fire lines without taking time to acclimate to the altitude.

"It was like breathing through a bag," said John "Doc" Brown, who spent the first two weeks supervising a crew from Medford, Ore. "It's a little bit harder doing this work because the air is so thin up there."

Typical symptoms of altitude sickness include severe headaches, lethargy, breathing difficulty and disorientation.

"We are getting a lot of people who are just not used to this altitude," said Tina Matiyow, the camp's medical management leader. "This is the most cases of this I've ever seen."

Evacuated Homes Being Looted

Officials said Friday that burglars have stolen items including tools and electronics from 10 homes that were evacuated.

The burglars mostly targeted subdivisions not under evacuation orders because those are the areas that are not being patrolled by sheriff's deputies, said a La Plata County Sheriff's Department spokesman.

Looting was not a problem in Jefferson and Douglas counties, where thousands of people were forced from their homes because of the 137,000-acre Hayman Fire.

Also this week, some Durango-area residents began receiving hoax evacuation calls. County officials warned people to be leery of evacuation calls that do not arrive on the county's automated reverse-911 system, which can call residents and play a recorded message.

"We also have deputies go house to house and drive through an evacuated area with their sirens on and a loudspeaker," said Joanne Spina, spokeswoman for the La Plata County Office of Emergency Management.

Re-Evacuation Orders Frustrate Many

Fueled by afternoon winds and lightning, the Missionary Ridge wildfire flared up on Thursday, forcing seven neighborhoods to re-evacuate.

Those living north of Vallecito Reservoir were told to leave their homes just hours after they were allowed to return home.

The weather calmed Thursday night, and some rain was reported overnight, but firefighters said there wasn't enough moisture to have an impact.

The fire remains only 30 percent contained, and there is no time estimate for full containment.

It has destroyed 57 homes and 600 others are threatened.

At least 1,100 homes are still evacuated.

On Friday, crews are focused on shoring up containment lines near homes on the northeast edge of the fire, as well as bolstering lines on the southwest flank near Durango, said fire information officer Dixie Dies.

A smaller fire 2 miles west of the main blaze known as the Valley Fire had scorched at least 400 acres and destroyed at least six structures. It is completely contained.

About 240 homes were evacuated because of that fire.

The Missionary Ridge Fire started June 9 from a discarded cigarette or ash, officials said. It was started beside Missionary Ridge Road.

To date, the cost of battling this wildfire is more than $18.5 million.

It is currently about 5 miles from the perimeter of Durango.