The 186 Fire, a 10-acre blaze burning east of Hermosa on Missionary Ridge, had not grown in size as of Wednesday afternoon.

Denise Alonzo, spokeswoman for the San Juan National Forest, said a helicopter, air attack plane, two air tankers and about 50 firefighters were working on the fire, which started Tuesday.

Alonzo said the largest concern Wednesday was an area with thick, heavy debris on the ground and “standing dead snags,” which pose a risk to firefighters. The debris was preventing firefighters from constructing a fire line in the area.

The fire has been contained by either fire-retardant or natural barriers, such as rocks, which have stopped its spread toward the east.

Fire personnel will use a heli-tanker Thursday to monitor the east side of the blaze. Alonzo said if the fire spreads to the east, crews have plans to safely engage it in a secondary location.

Firefighters are unlikely to completely extinguish the interior of the fire because of the dangers. Instead, they will build a containment line around the perimeter of the blaze and let the interior burn itself out.

“The public should expect to see smoke from the area for several days until the heavy material burns down, smolders, in the middle of the fire,” Alonzo said.

The fire posed no immediate threat to structures, and the weather is “positive” for fighting fires, she said Wednesday morning.

Additional resources will be brought in Thursday to prepare for anticipated lightning and thunderstorms.

The Forest Service says the 186 Fire is a lightning-caused fire, possibly a holdover from a thunderstorm June 5.

This is a developing story. Check back with www.durangoherald.com for updates.

bmandile@durangoherald.com