A grand jury has indicted three environmental activists for their roles in a July 2000 vandalism spree at a U.S. Forest Service property in northern Wisconsin.

The indictment announced Tuesday charges Katherine Christianson of Santa Fe, N.M., Aaron Ellringer of Eau Claire, Wis., and Bryan Rivera of Olympia, Wash.

Prosecutors say Christianson, Rivera and two others damaged government vehicles and 500 trees used for research at a Forest Service property in Rhinelander. Ellringer is accused of being their driver.

Prosecutors say the three are affiliated with the Earth Liberation Front and Earth First, groups that have used vandalism and arson to protest environmental practices.

Attorneys representing the three did not immediately return messages.