The Earth Liberation Front issued a statement on its Web site Thursday saying that the group considers graffiti left at the scene and an earlier fax to a Salt Lake City radio station as "a legitimate claim of responsibility."
The ELF, a loosely organized group of militant environmentalists, generally communicates with the media through e-mail. The Associated Press received Thursday's statement via e-mail, the contents of which were later posted on the Web site.
FBI spokesman Bob Wright said the group's reliance on e-mail and fax statements contribute to the difficulty of making an arrest. The agency has not ruled out that the statement and the earlier fax could be "red herrings," Wright said.
Authorities earlier said the arson had the hallmarks of an ELF attack.
The fax to the radio station said the lumberyard was targeted because it had ignored warnings to repair forklifts that emitted more pollution than diesel engines. The initials "ELF" were spray-painted on a building at the lumberyard and a truck. No one was injured.
The ELF has targeted lumberyards in the past, claiming they contribute to ecological destruction and sprawl.
The FBI says the ELF has caused more than $100 million in damage since 1996.
The group has been linked to arson and vandalism at agriculture research labs, logging operations, sport utility vehicle dealerships and construction sites. The costliest incident to date involved a $50 million fire last year that destroyed a five-story apartment complex under construction in San Diego.
By Alexandria Sage