Bomb Capable of Killing Hundreds Found on Martin Luther King parade route

A backpack bomb which could have killed hundreds has been disabled after being left along the route of a Martin Luther King memorial day parade in the U.S.

The device was spotted on the street in Spokane, Washington, by workers just 30 minutes before 1,500 people were due to walk past in celebration of the late black civil rights leader.

The FBI has so far declined to reveal specifics about the explosives but an official familiar with the case said the bomb was sophisticated and had a remote detonator.

Investigations revealed it had been set up to spray shrapnel right into the crowd and cause 'multiple casualties'.

The incident is now being treated as domestic terrorism by the FBI who said the the bomb was a 'viable device' akin to a pipe bomb and that white supremacists could be behind it.

'The potential for lethality was clear,' said Frank Harrill, the special agent in the charge of the Spokane FBI office.

'Suffice it to say it was of grave conce. You could describe it as an improvised destructive device...or improvised explosive device.'

He added that whilst there was no immediate motive 'the timing and placement of the backpack along the march route is inescapable.' 

The backpack was found just 30 minutes before 1,500 revelers arrived for the parade

This video screengrab shows a heavily armored worker working to dismantle the bomb

The Swiss-Army brand backpack was first identified on Monday moing in Spokane by workers on the march who notified the police and moved the route away from it.

It has been placed sitting upright on a metal bench against a brick wall to ensure that the explosion would have gone outwards, causing maximum damage to the crowd.

No waing had been issued about its location.

According to an FBI press release, 'subsequent preliminary analysis revealed the backpack contained a potentially deadly destructive device, likely capable of inflicting multiple casualties.' 

A scene of the Spokane parade route. The bomb could have killed hundreds of people

Investigators also found two T-shirts inside the backpack which they hoped would offer some clues to the identity of the suspect.

One read 'Stevens County Relay For Life June 25th-26th 2010' and another black T-shirt shirt had the slogan 'Treasure Island Spring 2009' on it.

The FBI's Inland Northwest Joint Terrorism Task Force has offered a $20,000 reward for information leading to the arrest and conviction of whoever made the device.

Some 15 different hate groups are in operation in Washington State including the racist Aryan Nations.

The FBI said those responsible are to be considered 'armed and dangerous'.