Photo of Tenn. Firefighters Resting for First Time in 36 Hours Goes Viral as Death Toll Reaches 13

The image was taken after wildfires forced thousands from their homes earlier this week.

An image depicting firefighters taking a rest from battling Tennessee's wildfires for the first time in 36 hours has gone viral.

"As close as we got to seeing sleep in 36 hours," Adam Scott Momberger, of Jonesborough, wrote on Facebook as he shared the image of his comrades lying on a sidewalk.

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The photo was taken after wildfires began in the Great Smoky Mountains National Park last week. A drought in the area and strong winds helped the fire spread, and by Friday, more than 17,000 acres had been destroyed by the flames.

At a press conference Friday, Sevier County Mayor Larry Waters said the death toll has climbed to at least 13, including one person who appeared to die of a heart attack. Dozens more have been injured.

Family members are desperately waiting for word about missing loved ones as first responders begin to search previously inaccessible areas.

On Friday, Gatlinburg residents were allowed to return to the resort town for the first time since more than 14,000 people were forced to evacuate Monday. It was their first chance to survey the damage close-up, from burned-down homes to wrecked cars.

Mayor Waters said that at least 1,000 buildings in the area were destroyed or severely damaged.

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"I can't describe to you the feelings we have over this tragedy," he said during a news conference.

Authorities believe someone is responsible for starting the fires, although it is not yet clear if it was intentionally set.

"There were no natural factors," Clayton Jordan, Deputy Superintendent for the Great Smoky Mountains National Park said at a press conference. "There were no lightning strikes that could have started this. So it's very obvious that this was a human caused fire."

Agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives are helping investigate the cause.

Watch: Aspiring Weatherman Started Forest Fire So He Could Report on It