(CNN) -- Fire engulfed five luxury homes Monday morning at a subdivision north of Seattle in what could be a case of ecoterrorism, officials said.
Firefighters attack blazes at luxury homes Monday in suburban Seattle, Washington.
A sign with the letters "ELF" was found at the scene of the fires in the "Street of Dreams" development in Woodinville, Washington, said Chief Rick Eastman of Snohomish County Fire District No. 7.
Eastman did not say if the sign is believed to be from the Earth Liberation Front, which the FBI has called an ecoterrorist group.
"Built green? Nope black!" the sign reads, according to an image from CNN affiliate KING-TV in Seattle. The sign calls the homes "McMansions." Watch why ELF is so elusive »
"My understanding is that it was an act of terror," Heller said.
The FBI said the fires are being investigated as an act of domestic terrorism.
Heller said he was out of town on business and was rushing back to see what was left of the development. He said it was a new subdivision that featured luxury homes priced at $2 million.
Video footage showed large grayish white plumes of smoke billowing in the air and firefighters trying to contain blazes in large homes in a heavily wooded area.
Eastman said there had been no injuries and there were no suspects. He told KING-TV that police and agents of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives were investigating.
Seattle's Street of Dreams is "the most popular and highest attended single site luxury home and garden tour in the U.S.," according to the event's Web site.
According to the FBI, the Earth Liberation Front claimed responsibility for burning five townhomes under construction on November 20, 2005, in Hagerstown, Maryland. Fire officials investigating the scene determined that kerosene was used as the accelerant in the arson, the FBI said.
Last year, 10 people, including self-proclaimed members of the ELF and members of another organization called the Animal Liberation Front, were convicted for a string of arson fires that totaled more than $40 million in damage, according to an August statement by the U.S. Justice Department.
At that time, the court case was called the "largest ecoterrorism case in U.S. history," according to the statement.
Three others charged in the case are at large and considered international fugitives by the Justice Department. E-mail to a friend