Four area newspapers have received letters claiming responsibility for the bombs by the Earth Liberation Front, or ELF, an environmental extremist group to which federal authorities attribute millions of dollars in arson-related destruction and numerous acts of vandalism in the United States. The letters threatened "one or more actions every few weeks."
In 1998, ELF destroyed four ski lifts and damaged a restaurant and other facilities at Vail Ski Resort in Colorado, causing $12 million in damage, authorities said, citing the group's claim of responsibility. In 2001, ELF said it started a fire that caused $3 million in damage to a horticulture laboratory at the University of Washington in Seattle perhaps targeted in the mistaken belief, university officials said, that the facility was being used for gene- splicing experiments. In 2003, two homes under construction near Ann Arbor, Mich., were set on fire by another cell of the group, authorities said.
ELF also has claimed responsibility for the August 2003 torching of a condominium complex under construction in San Diego, which resulted in $50 million in damage, according to the FBI. That month, ELF members also allegedly vandalized and set fire to more than 120 sport utility vehicles in West Covina, Calif. A graduate student at the California Institute of Technology was convicted in November for his role in the vandalism.