Denver ? Four alleged environmental extremists have been indicted in a 1998 firebombing at the Vail ski resort that caused $12 million in damage – one of the most devastating ecoterrorism attacks in U.S. history.

All four defendants had been named in an earlier indictment in Oregon charging them with conspiracy in a series of similar sabotage attacks in Oregon, California and Wyoming.

Named in the indictment are Chelsea Gerlach, 29, of Portland, Ore.; Stanislas Meyerhoff, 28, of Charlottesville, Va.; Josephine Sunshine Overaker, 31; and Rebecca J. Rubin, 33. Gerlach and Meyerhoff are in custody in Oregon. Authorities said the whereabouts of the others two were unknown.

The blaze left a mountain lodge, two restaurants and a few other buildings and ski lifts in smoldering ruins. A shadowy underground group calling itself the Earth Liberation Front claimed responsibility and said it had targeted Vail because it was expanding into potential habitat of the lynx, an endangered cat.