The Earth Liberation Front, a shadowy group blamed for costly arson attacks across the country, claimed responsibility Friday for fires last month at the University of Washington and a tree farm in Oregon.
The organization is stepping up efforts to punish companies and institutions it says are threatening the environment, the FBI said Friday.
Several hours before ELF's announcement, three logging trucks were torched at a company in Eagle Creek, 40 miles southeast of Portland. There was no immediate claim of responsibility.
The trucks were going to be used for harvesting trees at a nearby site in Mt. Hood National Forest.
In its announcement Friday, the ELF claimed responsibility for the fires May 21 at the Jefferson Poplar Farms in Clatskanie, Ore., and at the University of Washington Center for Urban Horticulture in Seattle. Both operations are developing hybrid poplar trees. The fire at the university caused as much as $3 million in structural damage; the Oregon fire caused at least $500,000 in damage.
FBI officials said the group is making good on a promise it made earlier this year to increase the violence. The agency considers the ELF one of the nation's most dangerous terrorist groups.