ST. LOUIS (AP) — Officials with the U.S. Forest Service are cautiously optimistic that a new treatment may help bats survive a deadly disease known as white-nose syndrome that has claimed the lives of millions of bats.

About 60 brown bats found with the disease last fall but successfully treated were released Tuesday at the Mark Twain Cave complex near the northeast Missouri town of Hannibal.

The disease has killed up to 6 million bats in 28 states and Canada, caused by a white fungus that appears on the noses of bats. Experts with the Forest Service and Georgia State University believe native soil bacteria produce natural volatiles that inhibit growth of the fungus.

They treated diseased bats in labs and found marked improvement in their health, including the bats released near Hannibal.