DURANGO, Colo. — A fire in the Lightner Creek area west of Durango in southwest Colorado forced mandatory evacuations Wednesday evening.

Firefighters were not sure if it started as a structure fire or wildland fire, but they said the initial structure involved was lost.

The fire was first reported shortly after 4 p.m. and was estimated at about 100 acres as of 7 p.m.

Evacuations were in place Wednesday night:

• All residents on County Road 207 north of the intersection of County Road 207/208;
• All residents on County Road 206, with the exception of the Westwood Apartments, at the intersection of County Road 206 and Highway 160;
• All residents on County Road 208;
• The Twin Buttes subdivision;
• Animas High School;
• All recreation trails in the Test Tracks west of downtown Durango are closed, including Hogsback, Leydon and Hidden Valley trails.

#lightnercreekfire #durangoco pic.twitter.com/wgSWPai8fi

— Julie Romero (@jbromero) June 29, 2017

The Colorado Office of Emergency Management said people in about 170 homes were asked to evacuate.

About 100 guests were evacuated from the Lightner Creek Campground, the camp host told the Durango Herald.

The La Plata County Fairgrounds was opened as an evacuation center for people and pets. Three heavy air tankers were ordered from Denver to help fight the fire.

A community hotline for the Lightner Creek Fire was established at 970-385-8700.