Two radio station towers near Seattle that have generated intense local opposition were toppled early Friday in an act of sabotage that bore the initials of the radical Earth Liberation Front.

The towers for KRKO-AM _ one of which was 349 feet tall _ were torn down because of health and environmental concerns, according to an e-mail from the North American ELF Press Office, which has represented the shadowy group in the past.

"We have to weigh our priorities, and the local ecosystem in Everett, along with the local residents, do not need additional sports news radio station towers that come at the expense of reduced property values and harmful radio waves," ELF press office spokesman Jason Crawford said in the e-mail.

The ELF is a loose collection of radical environmentalists that has claimed responsibility for dozens of attacks since the 1990s. A banner that bore the initials of the ELF was left at the scene, authorities said.

The FBI has taken over as lead investigator in Friday's incident, and agent Marty Prewett said authorities haven't found any evidence that other individuals or groups besides the ELF were involved.

The towers apparently were taken down with a track hoe, a piece of heavy construction equipment that was already on the site, Prewett said. Skotdal said part of the tower fell onto the track hoe and damaged the scoop mechanism.

"Whoever did it is lucky they didn't get killed," Skotdal said.

The ELF's Web site featured a picture of one of the towers lying on its site with the caption "Earth Liberation Front Topples Two Radio Station Towers in Snohomish County, WA," followed by the words: "Details coming soon."

Crawford told the AP by telephone he believed more than one person was involved. He said he had not spoken directly with anyone who claimed to be involved but received some e-mail from what appear to be locals who support the action.

The towers belonging to KRKO _ a family-owned station in Everett, about 25 miles north of Seattle _ have prompted complaints from neighbors of interference from radio signals on home telephone and intercom lines. The site for the towers is in the town of Snohomish, about eight miles southeast of Everett.

The station's plans to increase its transmission capacity by building more towers on the site have been embroiled for more than a decade in appeals and litigation over issues ranging from trumpeter swan habitat to potential health hazards to humans.

A neighbor told a 911 operator that someone seemed to be attacking the towers with a bulldozer or other heavy equipment at about 3:30 a.m., Snohomish County sheriff's office spokeswoman Rebecca Hover told The Herald of Everett.

Sheriff's deputies on Friday morning found the towers on the ground with heavy construction equipment nearby, Hover said.

The station remained on the air Friday after shifting to other transmission equipment. Skotdal announced a $25,000 reward for information leading to the capture and conviction of whoever was responsible.

"We'll use our airwaves to do it, too," Skotdal said.

The ELF has claimed responsibility for several arsons in the region, including a fire that destroyed the Center for Urban Horticulture at the University of Washington in Seattle in 2001.

An ELF sign was left at the scene of fires set on March 3, 2008, at a number of luxury houses in a development in Echo Lake, north of Seattle.

KRKO's additions to its existing towers in Snohomish were completed in February, allowing the station to boost its AM signal to where it could compete with larger broadcasters in the Seattle-Tacoma area. That's when the complaints from neighbors over telephone interference began.

The Skotdal family also plans to build two 199-foot towers at the same site for a new 5,000-watt AM station that would cover Snohomish County on another frequency.

A hearing examiner denied a permit for the towers, based on claims that radio signals could be dangerous to humans. But the council voted to reverse the finding, saying it was based on shaky scientific evidence.

A King County judge upheld the council's decision on Aug. 14.

Despite the long-running dispute, the attack was the first on the project, Skotdal said.

"When all legal channels of opposition have been exhausted, concerned citizens have to take action into their own hands to protect life and the planet," Crawford said in the e-mail.

Skotdal said the toppled towers should be up and operational again in the first or second quarter of next year, and he hopes to get the new signal on the air in the same time frame rather than later in the year, as planned earlier. Foundations being built for the new towers escaped damage, he added.

The action upset one of the leading opponents of KRKO's expansion plans.

"It has been a long legal battle and I'm upset to see this kind of violence happen here," Lee Bennett Jr., president of Citizens to Preserve the Upper Snohomish River Valley, told The Herald. "This is not the way to handle it."