SNOHOMISH – Federal agents have taken over an investigation into the destruction of two radio towers belonging to Everett radio station KRKO.

The towers were toppled early this morning and a group that practices ecoterrorism is laying claim to the act.

The toppled towers looked like a squashed Erector Set sitting in the farmlands of unincorporated Snohomish. About 50 yards away, a cloth banner was on a fence surrounding the towers.

On it was a message, apparently spray painted.

“Wassup? Sno Cty?” the sign read. “ELF.”

ELF is the acronym for the Earth Liberation Front. The sign also appeared to mention by name the Skotdal family, which owns the station.

KRKO General Manager Andy Skotdal was asked what he thought of the message.

“Other than the fact they don’t know how to spell?” he said.

Skotdal said he is offering a $25,000 reward to try to catch the people who knocked down his towers.

“We’ll use our airwaves to do it too,” he said.

About half a dozen FBI agents were on the scene this morning.

Local opponents were surprised by the destruction of the towers, which have been in use since July 2008. Two more towers, under construction, did not appear to be damaged by the vandalism.

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

Bennett said he also was surprised that heavy equipment alone could bring the towers down.

“I’m just amazed it came down,” he said. “Whether they did cutting before, I don’t know.”

Some at the scene speculated that one tower was pulled over by an excavator, while the other was pushed down. By mid-morning, the excavator remained entangled in the wreckage of one of the towers, although investigators have yet to confirm that it was used in the vandalism.

A neighbor called 911 around 3:30 a.m. to report that someone appeared to be using a bulldozer, or other heavy equipment, to knock the radio towers over, Snohomish County sheriff’s spokeswoman Rebecca Hover said.

The towers are in the 13400 block of Short School Road south of Snohomish. Deputies arrived to find a 349-foot tower and a 199-foot tower toppled. A police dog was used to try to track those responsible, but no suspects were caught, Hover said.

The deputies “found some other evidence at the scene,” she said. “That’s something that only the suspect or suspects would have information about.”

The Web site of the North American Earth Liberation Front press office, www.elfpressoffice.org, this morning posted a story about the radio tower’s toppling.

“Breaking news: Earth Liberation Front Topples Two Radio Station Towers in Snohomish County, WA.” the headline read.

“We have every indication to believe that it is in fact a legitimate ELF action,” said Jason Crawford, a spokesman for the ELF press office in Washington, D.C.

Crawford said he didn’t know who was responsible, nor had he heard directly from those responsible. Still, the action had the trademarks of his group, he said.

“When all other 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.

The radio station’s owner has dismissed environmental studies as junk science and been dismissive of opposition, the ELF spokesman said.

Ecoterrorists have a history of operating in Snohomish County. They are blamed for the multimillion-dollar fire that destroyed the Street of Dreams development near Echo Lake.

It doesn’t matter if the people responsible for the vandalism were directly linked to ELF or not, said Gary Perlstein, a professor emeritus at Portland State University who has studied the domestic terrorism group.

“If it goes along with their philosophy, then they will claim responsibility,” Perlstein said.

The action appears to be consistent with ELF’s effort to curb urban sprawl, he said. Like other ELF acts, the toppling of the radio towers appears well thought out and likely was coordinated weeks in advance, Perlstein said.

“These are not spontaneous acts,” he said. “They’re planned.”

While ELF typically doesn’t condone violence against people, communiqués have said ELF members “wouldn’t hesitate to pick up the gun,” Perlstein said.

That Skotdal apparently was named on the sign that was left behind is a reason for concern, the professor said.

“I hope the police are watching his home,” he said.

KRKO, a family-owned station, has been in a long battle with opponents of an addition to its existing towers east of Everett. Appeals and litigation over the towers have been going on for more than a decade.

On Aug. 14, King County Superior Court Judge Douglass North upheld a February land-use decision by the Snohomish County Council approving two 199-foot AM structures to be constructed next to three existing towers that occupy the site near Short School Road.

A 349-foot antenna also occupies the site.

S-R Broadcasting, parent company of KRKO-AM 1380, wanted the new antennae so it can transmit a new, stronger signal at 1520 AM.

Opponents of the towers filed the court appeal in March, claiming the Snohomish County Council did not follow proper procedure when it decided in February to let S-R Broadcasting build the towers.

The council overturned a hearing examiner’s decision to deny a permit for the towers, based on claims that radio signals are dangerous to human health. A majority of the council thought the hearing examiner’s decision was based on shaky scientific evidence.

Skotdal in March called the appeal “frivolous” and said the other faction had already exhausted the correct channels for dealing with the issue.

Tower opponents cited a range of studies claiming that AM radio waves have negative effects on people and wildlife — among them, increased rates of childhood leukemia and destruction of trumpeter swan habitat. People who live near the towers also had complained increasingly of radio signals coming over home phone and intercom lines since KRKO upped its broadcasting power in February.

This morning, the crime scene drew out curious opponents of the towers such as Elizabeth Grant, who has lived in the valley for 12 years.

“I just don’t know what to think,” she said. “It is hard to say who would really be responsible for this. It just goes to show people did not want this to happen in the valley.”

There was well-organized opposition to the project over a period of years, Grant said, but she added that it would be hard to imagine the local opponents being moved to topple the towers.

Skotdal earlier said he hoped the new signal would be on the air by year’s end. Today’s vandalism likely will just accelerate the timetable, he said.

The station today transferred its radio transmission and remained on the air.