RAPID CITY, S.D. (AP) — U.S. Forest Service officials say falling trees pose an increasing threat to hikers, bikers, campers and others in the Black Hills National Forest of western South Dakota and northeastern Wyoming.

The reason is that pine trees killed by mountain pine beetles on hundreds of thousands of acres are decaying and becoming more likely to tumble.

Forest Service official Dave Slepnikoff tells the Rapid City Journal (http://bit.ly/1aAox1d ) that windy days are particularly dangerous. His advice is for people in the forest to be aware of their surroundings and look up from time to time.

The Forest Service has removed some potentially dangerous trees near campgrounds and other high-traffic areas.