Federal law officers near Spokane have arrested at least one person in connection to a backpack bomb found at a Martin Luther King, Jr. Day parade, KHQ/6 reported Wednesday morning.

According to the television station report, they received a tip that nine FBI vehicles were seen speeding to a house in Colville. Two armored vehicles were also on the scene.

Additional details were not immediately available. The station had not noted why reporters believe the arrest was related to the MLK Day incident.

The bomb was found on Jan. 17 inside a backpack and placed on a bench before the parade started. The parade was rerouted as the bomb was defused.

Describing the bomb as sophisticated and designed to produce mass casualties, the FBI initially released photos of the backpack and of two T-shirts found inside. Spokane County Sheriff Ozzie Knezovich said he was told the bomb was mixed with shrapnel and also had a chemical component.

The bomb 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 from the public, but nothing that has allowed them to identify a suspect.

The T-shirts were both were tied to Stevens County, where Colville in located. One of the shirts was distributed in 2010 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.

While the FBI has remained quiet on the issue, civil rights advocates have described the incident as a hate attack.

"There is no question this was some kind of racist attack on black people and their supporters," said Mark Potok, a leader of the Alabama-based Southern Poverty Law Center, which battles hate groups. In its latest report, the SPLC found that eight of the nation's 1,002 active hate groups in 2010 had followers in the greater Spokane region.

Leaders of some local white separatist groups denied involvement in the bombing.