An underground fire burning along a coal seam in Colorado was discovered earlier this month, and officials said it's been ablaze for more than a year.

The fire was found Oct. 9 in the San Juan National Forest, around 15 miles northeast of the town of Dolores. The U.S. Forest Service said it's "been burning underground since summer 2018 when the Plateau Fire occurred."

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"The seam is extremely hot and will continue to burn for an indefinite period of time producing minimal amounts of smoke and a strong odor of creosote that will be noticeable," officials said in a news release Thursday. "The ground in and around the coal seam is extremely unstable and the area should be avoided."

As long as coal resources exist, the fire will continue to burn. The Plateau Fire from which the coal-seam fire was ignited was a wildfire that burned roughly 13 miles north of Dolores, in Montezuma County, from July to August in 2018. It burned 19,634 acres, officials said.

Forest officials said that in 2020, a team of experts will work "to gather data on the potential of underground resources present and predict the underground fire activity."

Patrick Seekins, of the Dolores Ranger District, told The Journal news outlet the fire is roughly one-tenth of an acre and is contained below ground.

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“When it was discovered, it was burning at low intensity above ground,” Seekins said. “A fire crew put out the surface fire in a little more than one day, but it continues to smolder and glow below ground."

Authorities couldn't figure out how the fire was sparked, until an investigation found the burning coal seam.

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Seekins said coal-seam fires typically burn out on their own once whatever is igniting it is used up. He said smoke is really only seen close to the coal-seam fire, but warned the public to avoid the area.

Anyone who sees the fire burning above ground in vegetation should call 911 or contact the Durango Interagency Dispatch at 970-385-1324.