Greenpeace officials say the group's climb atop a 700-foot smokestack was little more than a publicity stunt, but authorities have decided to make a federal case out of it.

The six Greenpeace activists who climbed the smokestack at the Hatfield's Ferry power station in Greene County Wednesday to protest President Bush's energy policy shuffled into U.S. District Court yesterday in handcuffs.

The six already face state felony charges of rioting, burglary and criminal trespass and three other lesser offenses. They found out yesterday that they also will be prosecuted in federal court for "destruction of an energy facility," the definition of which includes efforts to "interrupt" the function of a power plant.

"It's one thing to protest, which they are allowed to do, but it's quite another to impair the function of an energy facility," said U.S. Attorney Mary Beth Buchanan, who decided to file the charges after consulting with state police. "They put the facility workers and themselves in great danger. Their conduct warranted federal charges."

One of the six, Lynn Stone, 38, of Sorrento, Maine, said during a cell phone interview Wednesday from a perch about 50 stories up on the smokestack that the group never had any intention of shutting down the plant.

In fact, as they sat for hours on a walkway that stretches around the smokestack about 500 feet up, the plant continued to operate and the stack rained smoke down on the group.

The maximum penalty for conviction on that federal charge is 20 years in prison, although the protesters could end up merely paying fines and serving probation.

Josh Raisler Cohn, one of the six defendants, said he was surprised authorities were pursuing federal charges in addition to the state charges.

"I did not expect to receive serious federal charges for a nonviolent act of civil disobedience," said Raisler Cohn, 27, of Portland, Ore. "They're trying to intimidate people from participating in the democratic process, which includes peaceful protests."

Tom Wetterer, general counsel for Greenpeace, said the plant was never shut down and there was no property damage, so the federal charge isn't appropriate.

"I don't even think that statute would apply," he said.

The six climbers, who all wore orange T-shirts that said "Say No to Bush's Dirty Energy Scam," appeared before U.S. Magistrate Amy Hay, who told them to be back in court Thursday for a preliminary hearing.

In addition to Stone and Raisler Cohn, the protesters are Virginia Hunter, 43, of Los Angeles; Jessica Miller, 26, of Washington, D.C.; John Watterberg, 26, of Brooklyn, N.Y.; and Renee Blanchard, 24, of Washington, D.C.

Yesterday, all seemed generally unperturbed about their predicament, to the point of joking with the FBI agents who transported them to the U.S. Courthouse, Downtown. They smiled as U.S. marshals herded them down a hallway to holding cells to be processed.

Similarly, a clerk at the Waynesburg office of District Justice Lois Dayich said the activists were pleasant and polite when arraigned at 2:45 a.m. yesterday. They were released after posting 10 percent of $10,000 bond each.

Their preliminary hearing on the state charges is scheduled for July 26.

The protesters climbed ladders attached to the stack at the power station near Masontown, Fayette County, using mountain-climbing gear for safety, and then unfurled a huge banner denouncing Bush's energy policy.

It's not clear how they got on the property without being noticed by guards. No one at the plant knew about the invasion until a reporter for The Associated Press called the company.

The climbers descended Wednesday night and were taken into custody by state police. Federal agents also were on hand. State police had been in contact with the activists all day by phone and said they'd promised to turn themselves in.

Police said they didn't scale the tower to apprehend them because it would have been dangerous to both officers and activists.

Greenpeace targeted the coal-fired station, owned by Allegheny Energy, because the group says it is an example of the Bush administration's support of "dirty" energy technology over such clean sources as solar power.

"The Bush administration has systematically weakened clean air laws, placing the health of Americans and of the environment at risk," the group said in a statement.

Raisler Cohn said it was important to make a statement about the plant's pollution.

"Sometimes, it is really important for citizens to go to great lengths, or heights in this case, to get the message across," he said.

Greenpeace said it couldn't predict the outcome of the federal charges, but it noted the group recently was found not guilty in a similar federal prosecution in Miami in which activists who boarded a ship carrying mahogany harvested in a Brazilian rainforest were charged under an 1872 law intended to halt brothels from luring ship's crewmen ashore.