Whatever is killing the bats of New England appears to have arrived in Pennsylvania.

And New Jersey officials are checking out reports that it might be there, too.

Yesterday, the Pennsylvania Game Commission confirmed that bats had tested positive for the same fungus found in New England bats that have been dying by the tens of thousands during the last two winters.

Everyone agrees that the finding could have profound effects on the bat population here. One of the many mysteries is whether the fungus causes the deaths, now referred to as "white-nose syndrome," or is a symptom.

Biologists in 20 states, two Canadian provinces, several universities and numerous agencies have been working feverishly to get answers, said Jeremy Coleman, a biologist with the U.S. Fish and Wildlife Service field office in Cortland, N.Y.

Mass deaths have consequences not only for the bats, which are common throughout the region and are found even in urban areas.

"Bats are the best friends we have, in terms of insect control in some areas," said game commission spokesman Jerry Feaser. "And they are, for farmers, some of the best natural predators of crop-killing bugs."

A single bat can eat hundreds of mosquitoes and other insects an hour.

"If it weren't so tragic, it would be phenomenally interesting," said DeeAnn Reeder, a Bucknell University biologist and bat expert.

It was she, along with game commission biologist Greg Turner, who made the Pennsylvania discovery.

Fearing the fungus - and the syndrome - would spread to the state, officials began an intense monitoring program last summer. It included checking bat maternity colonies for signs of mortality and netting bats to check for abnormalities.

By October, when the bats had fattened to plumpness and were swarming outside the caves where they hibernate, "everybody looked good," Reeder said yesterday. "Their weights looked good. Their overall body condition looked good. We thought everyone was going to be OK."

The two researchers attached buttonlike sensors to some bats to collect information about each animal's body temperature.

Two weeks before Christmas, Reeder and Turner visited one of the sites, a former iron mine in Mifflin County, southeast of State College. All was still well.

A week later, they were shocked to see that 6 percent of the bats had the "classic" fungus on their noses and ears.

And a few were moving closer to the entrance.

So they collected some of the bats and sent them for testing at the National Wildlife Health Center in Wisconsin.

By Jan. 12, 45 percent of the mine's colony had moved toward the entrance.

In New Jersey, biologists also are seeing some of the symptoms and are investigating, said Darlene Yuhas, a spokeswoman for the state Department of Environmental Protection.

"It sounds bad," said Melissa Behr, a veterinary pathologist with the Wisconsin Veterinary Diagnostic Lab.

She did early work on white-nose syndrome, and the theory that she and others put forward in a paper published last fall in the journal Science was that the fungus was causing the bats to wake up from hibernation and groom.

The species affected, the little brown bat, is a quarter to a third the size of a mouse, she said, and it has little in the way of fat reserves.

"If they wake up and use that fat, their little body sensors tell them, 'We need to move out of this cave to get food.' "

In New York, where the syndrome first appeared in the winter of 2006-07, "they started coming out about this time, in January and February," Behr said. "And of course, in frigid weather there are no insects. And with no body fat, it's a death sentence."

The syndrome later spread to Vermont, Massachusetts and Connecticut. But there, as in New York, biologists did not start to investigate until after the bats died, which is when they found the fungus.

In Pennsylvania, biologists have found the fungus, but there have been no die-offs. Yet.

Are they seeing something new, or are they simply lucky enough to be getting data on what happens first, before the die-offs?

"We don't know," said the game commission's Feaser. "Bats have survived for more than 50 million years because they are tough mammals," Lisa Williams, a game commission wildlife diversity biologist, said in a statement. "But they have become increasingly vulnerable," largely because of habitat loss.

"White-nose now presents more uncertainty for bats," Williams said. "Quite frankly, we not sure yet that we can help them survive this threat."

Why, or where it came from, is still another mystery. Behr said that bats in Europe carry a similar fungus on their noses, although it doesn't appear to harm them.

It's possible, she said, that someone visited a cave there, then came home and went to another cave in Albany County, N.Y., where the syndrome seems to have started. The bats here might not have had resistance to to the fungus.

Officials are asking anyone who sees flying bats or dead bats this winter to report it to the regional game commission office in Reading at 610-926-3136.

Contact staff writer Sandy Bauers at 215-854-5147 or sbauers@phillynews.com.