Investigators said Thursday they have made an arrest in one of three recent alleged eco-terror arsons or attempted arsons east of Sacramento (search).

Ryan D. Lewis, 21, was arrested Wednesday at his home in Newcastle and charged with the Jan. 12 attempted firebombing of a commercial building in the nearby city of Auburn, northeast of Sacramento.

The FBI and U.S. attorney's office said the arson attempt was believed to have been committed on behalf of the Earth Liberation Front (search), a shadowy environmental extremist group.

No arrests have been made in a similar attempted firebombing at a subdivision in nearby Lincoln Dec. 27, or in an arson at an apartment complex in Sutter Creek to the south Feb. 7.

The FBI said its Joint Terrorism Task Force (search) is continuing its investigation.

The five incendiary devices found at the Auburn commercial complex matched three devices found in homes in the upscale Lincoln subdivision, the FBI has said.

Letters to several newspapers purporting to be from the Earth Liberation Front said the attempted Lincoln arson was a statement against suburban sprawl, while the Auburn office building was targeted as "a statement against work and the horror of the (cubicle)."

The letters promised more actions "every few weeks."

None of those devices exploded, but seven crude explosive devices at the Sutter Creek apartment complex caused an early morning blaze. Fire sprinklers helped minimize the damage.

Nearby graffiti asserted that "We will win -- ELF," investigators said.

The FBI says ELF has caused more than $100 million in damage since 1996, including an arson at a five-story condominium under construction in San Diego in August 2003 that caused $50 million in damages.