This story originally aired on Nov. 13, 2005.
When they first emerged in the mid-1990s, the environmental extremists calling themselves the "Earth Liberation Front" announced they were "the burning rage of a dying planet."
Ever since, the ELF, along with its sister group, the Animal Liberation Front, has been burning everything from SUV dealerships to research labs to housing developments.
In the last decade, these so-called "Eco-terrorists" have been responsible for more than $100 million in damages. And their tactics are beginning to escalate.
Some splinter groups have set off homemade bombs and threatened to kill people. As correspondent Ed Bradley first reported last November, things have gotten so bad, the FBI now considers them the country's biggest domestic terrorist threat.
The biggest act of eco-terrorism in U.S. history was a fire, deliberately set on the night of August 1, 2003, that destroyed a nearly-completed $23 million apartment complex just outside San Diego. The fire was set to protest urban sprawl.