A federal complaint provided no details of the investigation or what led to the arrest of Kevin William Harpham nearly two months after city workers found the bomb, which had been left in a backpack Jan. 17 on a bench. The city workers alerted authorities, and the device was defused without incident.

Harpham, 36, of northeastern Washington, who has been tied to a white supremacist organization, waived his right to a bail hearing as he made an initial appearance in U.S. District Court in Spokane Wednesday.

He has been charged with one count of attempting to use a weapon of mass destruction and one count of possessing an unregistered explosive device in a case the FBI has called an act of domestic terrorism.

Harpham, who was shackled at the ankles in court, will remain in the Spokane County Jail unless he changes his mind and asks for bail. A grand jury will meet March 22 and could issue an indictment.

Wearing a black sweatshirt with a Wells Fargo logo, and blue jeans, the unshaven Harpham gave yes and no answers to a series of questions from U.S. Magistrate Cynthia Imbrogno.

An FBI affidavit made in support of the charges remained under seal, and a federal public defender assigned to represent Harpham said he did not know if the government was pursuing other suspects in the case.

"The safety of our city has been of grave concern ever since Jan. 17," said Spokane Mayor Mary Verner, who expressed relief that an arrest had been made. "We are not going to let this incident define our community."

Attorney General Eric Holder, at a news conference on a different subject in Washington, D.C., said the bomb was operational.

"It was a viable device, it was planted with the aim of hurting or killing people," Holder said.

Harpham was arrested at a rural home near the town of Addy, about 20 miles south of Colville. There was no telephone listing for a Kevin Harpham in the general area.

A neighbor who told KHQ-TV of Spokane that he saw Harpham being taken into custody Wednesday morning said a vehicle was put on a trailer and removed by federal agents.

Kevin Coy described Harpham’s home as a trailer with lots of dogs around.

A federal law enforcement official, speaking on condition of anonymity and declining to provide additional details because the case is ongoing, said Harpham was a white supremacist.

The Southern Poverty Law Center, which tracks hate groups across the nation, also said they have a record of him being a member of the white supremacist National Alliance in 2004. But the neo-Nazi group has fallen on hard times since the death of its founder William Pierce in 2002, Potok said.

"We don’t know when he joined or if he remains a member," said Mark Potok of the Alabama-based SPLC.

Pierce was author of "The Turner Diaries," a novel about a future race war that was influential in the white supremacist movement.

Erich Gliebe, chairman of the National Alliance, based in Hillsboro, W.Va., told The Spokesman-Review newspaper of Spokane that Harpham is not a member of his organization, which he said believes all races are entitled to their own living spaces.

"We have a zero tolerance policy regarding illegal activity and anyone committing those acts – even hinting or joking — would not be welcome in our organization," Gliebe said.

"The bombing attempt in Spokane demonstrates that the threat of domestic terrorism from elements of the radical right is very real. And the threat may be growing," said J. Richard Cohen, president of the SPLC, in a press release.

Last month, the group released a report showing that hate groups now number more than 1,000 for the first time, including eight in the greater Spokane region.

For weeks, the FBI had said nothing about possible suspects in the Spokane case, but public opinion from the beginning focused on white supremacist groups. The area once served as headquarters for Richard Butler’s Aryan Nations, whose members were lured by the small number of minorities.

The bomb, which contained shrapnel and a chemical component, was sent to an FBI lab in Quantico, Va., and the agency offered a $20,000 reward for information from the public. The FBI has said it received plenty of photos and video tips, but it wasn’t clear if any led to the arrest. Investigators have said that two T-shirts found inside the backpack were linked to Stevens County.

One of the shirts was distributed last year at the "Relay for Life" race in Colville. The second shirt — which had the words "Treasure Island Spring 2009" on the front — was from a local theater production in 2009 in the town of Chewelah.

Afterward, federal public defender Roger Peven said he had met only briefly with his client. Peven said he didn’t think Harpham was married, and that they did not discuss white supremacist topics.

The U.S. Army said Harpham was a soldier at Fort Lewis, near Tacoma, Wash., from 1996-99.

A voice mail message left at a phone number associated with Harpham was not immediately returned.

Gov. Chris Gregoire on Wednesday again commended the three workers who found the bomb.

"It was clear that when the emergency response system was put to a test, it worked as it should have and prevented what could have been a terrible tragedy on a day of celebration," Gregoire said.

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Johnson reported from Seattle. Associated Press writer Pete Yost in Washington contributed to this report.