MLK Parade Bomb was Sophisticated, New to U.S.

Updated at 4:45 p.m. ET

SPOKANE, Wash. - A bomb left along the route of a Martin Luther King Jr. Day parade was a sophisticated explosive that had a remote detonator and the ability to cause many casualties, an official familiar with the case said Wednesday.

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The bomb, which was defused without incident on Monday, was the most potentially destructive he had ever seen, said the official, who spoke on condition of anonymity because he is not authorized to release information about the investigation.

"They haven't seen anything like this in this country," the official said. "This was the worst device, and most intentional device, I've ever seen."

CBS News Correspondent Bob Orr reports the bomb was planted to send the brunt of the blast directly toward those participating in the parade.

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The FBI said it has no suspects in the case and has asked the public for help in identifying anyone who might have been seen in the downtown area where the bomb was found.

The FBI on Wednesday declined to reveal any details about the bomb, which was spotted by three city employees about an hour before the parade was to start, said Frank Harrill, special agent in charge of the Spokane office. The employees looked inside, saw wires and immediately alerted law enforcement, and the parade was rerouted.

The FBI received no warnings in advance and no one has claimed responsibility for planting the bomb, Harrill said.

The bomb was contained inside a black backpack made by Swiss Army, and the FBI released a photo of the backpack as it sought information from the public. Also released were pictures of two T-shirts found in the pack. There was a gray T-shirt with writing for the Stevens County Relay for Life race last June. Stevens County is just north of Spokane County. The other dark T-shirt said Treasure Island Spring 2009.

The FBI and local officials have praised as heroes the city workers who spotted the backpack and quickly called police. Police were also hailed for immediately deciding to reroute the parade. The several hundred marchers, including many children, were not told why the route was changed.

Harrill said the FBI has received some leads since offering a $20,000 reward for information on Tuesday. But the agency can't discuss the leads publicly, he said.

There were no notes in the backpack, which has been shipped to an FBI lab in Quantico, Va., Harrill said.

Investigators are also seeking anyone who took photographs or video in the area between 8 a.m. and 11 a.m. on Monday.

Investigators have said the bomb was carefully placed on a metal bench with a brick wall behind that would have directed shrapnel toward Main Street, where marchers were expected to pass.

Spokane County's Board of Commissioners on Wednesday denounced the attempted bombing.

Commissioner Mark Richard, who spoke at the King celebration and did not learn until later about the bomb, expressed concern about the number of people who could have been injured or killed if it had detonated.

"Hundreds of people, including children, gathered to celebrate and recommit their lives to the cause of human rights," Richard said.

"The confluence of the holiday, the march and the device is inescapable, but we are not at the point where we can draw any particular motive," Harrill said.

Spokane, which has 200,000 residents, is about 100 miles south of the Canadian border, which is a particularly remote and heavily forested stretch used by drug smugglers and human traffickers.

Another explosive device was found March 23 beside the Thomas S. Foley U.S. Courthouse in downtown Spokane. No arrests have been made in that investigation, Harrill said, and agents didn't know if the two incidents were related.

The Spokane region and adjacent northern Idaho have had numerous incidents of anti-government and white supremacist activity during the past three decades.

The most visible was by the Aryan Nations, whose leader Richard Butler gathered racists and anti-Semites at his compound for two decades. Butler went bankrupt, lost the compound in a civil lawsuit in 2000 and died in 2004.

In 1996, white supremacists placed a pipe bomb outside City Hall in Spokane. The bomb exploded, blowing out a window and sending nails and screws across the street into Riverfront Park. There were no injuries. Two men arrested for the blast said it was part of a plot to spark a revolution and set up a whites-only nation.

In December, a man in Hayden, Idaho, built a snowman on his front lawn shaped like a member of the Ku Klux Klan holding a noose. The man knocked the pointy-headed snowman down after getting a visit from sheriff's deputies.

Harrill called the planting of the bomb an act of domestic terrorism that was clearly designed to advance a political or social agenda.

"The potential for injury and death were clearly present," he said.