(CNN) -- Authorities have a suspect in custody in connection with a backpack bomb found in January along a Martin Luther King Jr. Day parade route in Spokane, Washington, according to Michael Ormsby, U.S. attorney for the Eastern District of Washington.
Kevin William Harpham, 36, of Colville, Washington, was charged with attempted use of a weapon of mass destruction and possession of an unregistered explosive device, Ormsby said.
Harpham appeared before a federal magistrate Wednesday and was ordered held without bail after Harpham waived his detention hearing, Ormsby said. Federal public defenders were appointed to represent him, and they will be able to ask for a bail hearing at a later date, Ormsby told CNN.
Harpham lived alone in a mobile home or modified mobile home on a 10-acre tract in rural Stevens County, and the closest large city is Colville, Washington, Ormsby said.
Federal prosecutors will seek a grand jury indictment against Harpham on March 22, Ormsby said.
An arraignment for Harpham is scheduled for March 23, added Ormsby.
On Wednesday, authorities were conducting a search of Harpham's home, Ormsby said.
The weapon of mass destruction charge would carry a maximum penalty of life in prison, a $250,000 fine and up to five years of court supervision after release, prosecutors said. The unregistered explosive device charge would carry a maximum sentence of 10 years in prison, a $250,000 fine and up to three years of court supervision after release, they said.
The suspect was apprehended away from his home, a law enforcement source told CNN.
Authorities are trying to determine if the bomb attempt was part of a conspiracy, but for now, the scheme seems to be a "lone wolf" situation, the source said.
In January, the FBI said it would consider recent local neo-Nazi activity in its investigation of the backpack bomb.
But this week, authorities still have not publicly linked the bombing attempt to any specific group or organization, Ormsby said.
The bureau has been looking into the incident as "an act of domestic terrorism," Frank Harrill, special agent in charge of the FBI's Spokane field office, said in January.
The investigation was aided by detailed forensic and follow-up work on the backpack bomb itself, the law enforcement source said. After the bomb was discovered, it was sent to the FBI lab in Quantico, Virginia, authorities said at the time.
The bomb was found the morning of the parade in January by three workers before the event began, authorities said. The FBI released photos of the Swiss Army-brand backpack and two T-shirts found in it. One shirt says "Treasure Island 2009" and the other reads "Stevens County Relay For Life June 25th-26th 2010."
On Wednesday, Washington Gov. Chris Gregoire credited the three workers and law officers, saying when the Spokane's 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."
"I again want to commend the three workers who reported the suspicious backpack to authorities, and the law enforcement officers who responded," Gregoire said in a statement.
Also on Wednesday, U.S. Attorney General Eric Holder expressed gratitude no one was injured in the bombing attempt.
"I can say that it was a viable device. It was planted with the aim of injuring or killing people. And we were fortunate that it did not go off and people were not killed. We were just lucky in that regard," Holder said.
The device contained a chemical found in rat poison and was packed with little metal pellets, apparently as shrapnel, another law enforcement official told CNN in late January. The device was set up to be detonated remotely, that official said.
The two neo-Nazi activities the FBI referred to in January occurred in nearby Coeur d'Alene, Idaho -- one on the King holiday and another three days earlier. Coeur d'Alene is 35 miles east of Spokane.
Three days before the holiday, a handful of neo-Nazis in Coeur d'Alene protested two Mexican restaurants with signs saying, "This is white land" and "We want you out of here."
During the evening of the holiday, about 15 neo-Nazis demonstrated outside the Human Rights Education Institute in downtown Coeur d'Alene.
The Coeur d'Alene area had been a hotbed of neo-Nazi activity through the Aryan Nations and Order II hate groups since at least the 1970s, though the groups were disbanded through criminal convictions and civil lawsuits by 2000, said Tony Stewart, one of the founders of the Kootenai County Task Force on Human Relations in Coeur d'Alene.
CNN's Patrick Oppmann contributed to this report.