Four multimillion-dollar show homes from a suburb north of Seattle were engulfed by flames on Monday.

According to officials, a sign from a radical environmental group was found at the scene.

The sign bore the initials of the Earth Liberation Front group. According to video images of the sign aired by KING-TV, it was mocking the claims that the luxury homes on the “Street of Dreams” were environmentally friendly.

The sign said: "Built Green? Nope black!" the Associated Press reports.

The fires began at a part of model homes, unoccupied and furnished luxurious where the latest in high-end housing, interior design and landscaping are presented by developers. The homes are sold later on.

According to Chief Rick Eastman of Snohomish County District Seven, the fires were set in many places in different houses, looking suspicious.

He confirmed the fact that the ELF sign was found at the scene of the fires in the community north of Woodinville. Here some of the homes are still under construction.

Earth Liberation Front is a loose organization made out of radical environmentalists which was found in 1992 in the United Kingdom and spread to Europe by 1994.

Now is an international movement with actions in over a dozen countries.

In 1996, on Columbus Day, the ELF made its first appearance in the United States through some actions made at a public relations office and a McDonald’s restaurant in Oregon.

Authorities say that they are also responsible for other arsons in the Northwest.

A woman is on trial in Tacoma for a fire at the University of Washington in 2001 which was possibly the work of ELF.

Briana Waters, a 32-year-old violin teacher, is accused of letting her friends put a fire bomb.

The fire is one of the most famous and is part from a string of arsons which according to investigators were committed from the mid-1990s to 2001 by ELF.

No one was injured during the arson at the University of Washington, but its Center for Urban Horticulture had to be rebuilt with $7 million as it was destroyed.

The investigators said that it was the target of the ELF because its members thought it was the place where researchers were genetically engineering trees.