"The fungus is in some way involved in causing the bats to starve to death," biologist Thomas Tomasi of Missouri State University in Springfield said.

"They are burning up too many calories, at a rate faster than they can sustain," he said.

However, bat experts are not sure if the fungus caused the widespread deaths or is just an opportunistic microorganism infecting animals that were already weakened by some other threat, the Los Angeles Times reported Friday.

Scientists identified the white fungus as a formerly unknown strain of Geomyces -- fungi that live in soil, water and air and thrive at low temperatures.

Researchers had trouble isolating it because it disappeared when the dead animals warmed up in the laboratory. It could only be grown if kept cold, the Times said.

The epidemic, which bears similarities to a colony-collapse disorder that has decimated the U.S. honeybee population, first appeared in a cave near Albany, N.Y., in 2006.

It has since spread to at least four New England states, with 80 percent to 100 percent of bats dying in some caves.

The affected animals become severely emaciated, often emerging from their hibernation caves in the winter in a futile search for food, researchers say.