Marie Mason, 46, of Cincinnati; and Frank Ambrose, 33; Aren Burthwick, 27; and Stephanie Fultz, 27, all of Detroit, face federal arson charges. The university, FBI and U.S. attorney's office announced the arrests at a news conference at Michigan State.

The fire on New Year's Eve 1999 did about $1 million in damage to a genetics engineering lab at Michigan State in East Lansing, Mich. The next day, equipment used for commercial logging in northern Michigan was vandalized.

"This was more than an attack on a building and the destruction of valuable property. It was an assault on a core value of free and open inquiry at a research university," Michigan State University President Lou Anna Simon said.

ELF, a loose network of radical environmental activists, took responsibility for the attacks immediately. But James Dunlap, Michigan State police chief, said that investigators spent eight years tying the crimes to specific people.