(CNN) -- A suspect in the attempted bombing of a Martin Luther King Jr. Day parade in Washington state pleaded not guilty to the crime in U.S. Magistrate Court Wednesday, according to a federal law enforcement official.
Kevin Harpham, 36, of Colville, Washington, made the plea during an arraignment hearing in federal court in Spokane. Harpham faces trial on charges of attempting to use a weapon of mass destruction and for possessing an unregistered explosive device.
Federal authorities arrested Harpham March 9, nearly two months after the January 17 discovery of a backpack containing a bomb along the Martin Luther King Day parade route in Spokane. The explosive device was found and disabled before the event began.
Officials called it an incident "of domestic terrorism" that could have resulted in "mass casualties," had the bomb gone off.
If convicted, Harpham could face a maximum sentence of life in prison and a $250,000 fine, prosecutors say.
According to the Southern Poverty Law Center, which monitors extremist groups, Harpham frequently posted incendiary comments on white supremacist websites.
In 2004, according to the Poverty Law Center, Harpham allegedly stated, "I can't wait till the day I snap," in a posting on the white supremacist website the Vanguard News Network.
Harpham also allegedly wrote, "Those who say you can't win a war by bombing have never tried," according to the SPLC, which attributed more than 1,000 postings to the accused would-be bomber on the Vanguard website.
Vanguard advertises itself on the site as "No Jews. Just Right."
Although the posts did not carry Harpham's name directly, Law Center officials said they had come to know him by his writing, and recognized his work as it appeared online.
CNN's Patrick Oppmann contributed to this report