SPOKANE, Wash. (AP) - The two T-shirts found with a bomb placed along a Martin Luther King Jr. Day parade route in Spokane both came from the same nearby county.
The FBI released photos of the shirts found inside a backpack containing the bomb, which was discovered on a bench Monday before the parade started and was defused without incident.
One of the shirts was distributed last year at the "Relay for Life" race in Colville, the seat of Stevens County.
The origin of the second shirt - which had the words "Treasure Island Spring 2009" on the front - wasn't immediately clear. But after the photos were released, residents called the FBI and media to report the shirt was from a local theater production in 2009 in the town of Chewelah, 50 miles north of Spokane.
Colville and Chewelah are both in Stevens County, which borders Spokane County and has about 40,000 residents. The FBI declined to comment on whether it was focusing on the rural county.
"We're not going to comment on specific investigative angles," said Frank Harrill, who heads the FBI office in Spokane.
"This investigation is and will remain wide-ranging," Harrill said. "It's premature to attempt to assume any particular direction.
Tips from the public continue to pour in, and the search for the bomber could be lengthy, he said.
The bomb was placed on a metal bench with a brick wall behind that would have directed shrapnel toward Main Street, where marchers were expected to pass, investigators said.
Three city workers spotted the backpack about an hour before the parade was to start. They looked inside, saw wires and alerted law enforcement.
The bomb had a remote detonator and could have caused mass casualties, officials said.
The FBI has said the attempt on the day set aside to honor the slain civil rights leader raised the possibility of a racial motive.
Leaders of two local white supremacist groups have denied they were involved.
"The Aryan Nations does not advocate any violence," said Jerald O'Brien, leader of the group based in nearby Coeur d'Alene, Idaho. He said he has not been contacted by the FBI.
Meanwhile, Shaun Winkler of the White Knights of the KKK in northern Idaho said his group did not plant the bomb and that its members prefer distributing propaganda to going to prison.
Harrill said the backpack and T-shirts are being analyzed at an FBI lab in Quantico, Va.
The FBI has offered a $20,000 reward for information from the public.