DENVER (AP) — Extreme fire danger prompted officials to shut down a sprawling forest that includes some of Colorado's most stunning mountains in a region that attracts tourists from around the world, a rare tactic also being used in neighboring states as the U.S. Southwest struggles with severe drought.

National forests and parks in Arizona and New Mexico have already been shut down as precautions.

San Juan National Forest officials in southwestern Colorado closed hundreds of miles of trails and thousands of miles of back roads to hikers, bikers, horseback riders and campers Tuesday to prevent...