(AP) — The U.S. Forest Service is letting people visit caves in national forests and grasslands in the Rocky Mountain region again, but there are restrictions as officials work to halt a disease that has killed 5.5 million bats since 2006.

The agency issued a closure order in 2010 to keep white-nose syndrome from spreading. So far, the disease and the fungus that causes it haven’t been confirmed in the region, which covers Colorado, Wyoming, South Dakota, Nebraska and Kansas.

As of Thursday, people can visit the region’s caves but have to register first. They must decontaminate clothing and gear before and after entering caves. Gear used in caves or mines in states affected by white-nose syndrome is prohibited.

Caves used for winter hibernation will close from roughly Oct. 15-April 15.