ECHO LAKE — The images of flames eating away at homes and the possibility the destruction was the work of environmental extremists ignited old anger for Mark Verbarendse.

The Camano Island man’s dream home was near completion when it was torched in 2006 in what authorities believe was an act of eco-terrorism. A bedsheet marked with the initials ELF — short for Earth Liberation Front — was found at the fire scene.

“We’ve been there, on the receiving end of that statement,” Verbarendse said Tuesday. “My heart goes out to those builders and the families who may have planned to live there. I know that feeling. There are real people behind these homes. It isn’t just that a house burned and insurance will cover it. People could lose their jobs. People, the firefighters, could have lost their lives.”

Federal investigators had not determined whether ELF is responsible for the arsons that caused $7 million in damage Monday to a neighborhood of unoccupied luxury homes near Echo Lake.

A banner found near the homes contained an anti-­development message along with ELF’s initials. It was similar to one left on Verbarendse’s property.

The similarities between the fires are under investigation, and the banner found Monday is being scrutinized by forensic experts for clues, said Kelvin Crenshaw, special agent in charge for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

“The banners are the consistent things. I think that is far as I’m willing to go,” he said.

Federal agents have begun the complex process of picking clues from the rubble.

“This case is going to turn on forensics and possibly a cooperative witness,” said Dave Gomez, the FBI Seattle assistant special agent in charge.

Investigators are calling the arsons potential acts of domestic terrorism but aren’t ruling out other potential explanations, officials said.

Contrary to reports at the scene Monday, firefighters did not find evidence of explosive devices inside the unoccupied houses, Crenshaw said. Instead, the fires appeared to have been set using items found inside the homes.

“It’s paper. It’s wood. Whatever you can gather together and light a match,” Crenshaw said.

The arsonists may have shied away from using incendiary devices. Convictions linked to the devices could carry a mandatory 30-year prison sentence, Gomez said.

Monday’s attack is the first connected to ELF in the Puget Sound area since the Camano Island fire that destroyed Verbarendse’s home, Gomez said.

Acting in secrecy, ELF members resort to violence to further their brand of environmental activism. There isn’t a leader; people generally operate in small, autonomous cells.

“It’s not an organization like we think of one,” said Gary Perlstein, a criminology professor at Portland State University in Oregon who has studied and written about the group.

Nationwide, radical environmentalists have threatened lives and caused more than $200 million damage in recent years, Gomez said. Some of those targeted have been attacked by mistake.

Monday’s fires ranked high among arsons potentially linked to ELF.

“It’s one of the bigger ones as far residential fires,” said Nick Starcevic, an ATF spokesman.

Three of the homes, part of the 2007 Street of Dreams, were destroyed. Smoke damaged two other homes. All five were built to be more environmentally friendly and appeal to a “green” customer, builders said.

Environmental activism has a long history in the Western states, which might explain the onslaught of arsons and sabotage attempts conducted under ELF’s banner, FBI spokesman Fred Gutt said.

In Snohomish County, ELF is thought to be responsible for fires that destroyed two homes in Snohomish in 2004, as well as attempts at several other housing projects, including one not far from Monday’s arsons.

At least one confirmed ELF member grew up here.

Zachary O. Jenson, a 2003 graduate of Monroe High School, pleaded guilty to conspiracy in July 2006 in a California federal court after admitting he took part in a plot to blow up a dam and a fisheries building as part of an ELF cell operation.

Jenson has been free on bail, living in Seattle for more than a year awaiting sentencing, according to court documents.

Gutt didn’t know if investigators plan to question Jenson about Monday’s fires.

“We haven’t ruled anyone out or in,” he said. “We don’t hound someone for past deeds. On the other hand, wherever the evidence takes us, it takes us.”

If the arsons are the work of ELF, someone likely will send out an e-mail to the media within the week to take responsibility, Perlstein said. By Tuesday afternoon, there was no word from the group.

The fires and tactics match past ELF arsons, Perlstein said.

He suspects that the ongoing criminal prosecution of people accused of the 2001 firebombing of the University of Washington’s horticulture center and the extradition from Canada of an Oregon man accused of sabotaging logging and cement trucks may have sparked Monday’s arsons.

The Street of Dreams homes also may have been targeted to further an anti-development message, he said.

Snohomish County has been one of the state’s fastest growing in the past decade. Between 3,500 and 5,325 single-family homes have been permitted each year in the unincorporated areas of the county since 1994, peaking in 2005.

Controversy has followed the rural and urban growth. County officials have turned to tweaking building regulations while some anti-growth advocates call for bans and an overhaul of the rules.

Local environmentalist groups condemned Monday’s arson.

“This is a criminal act and we’re definitely opposed to such actions. We’re very sad that people lost property,” said Kristin Kelly, a spokeswoman for Futurewise, an anti-development group. “It’s not a way to solve any kind of problem.”

Futurewise works within the parameters of the law to make changes in land-use policy, she said.

“Burning down homes is no the way to solve the problem,” she said.

Reporter Jeff Switzer contributed to this report.

Reporter Diana Hefley: 425-339-3463 or hefley@heraldnet.com.