"There were no reported injuries in the three-alarm blaze that started around 4:00 am local time Monday," Snohomish County fire department official Rick Eastman told AFP.

"Some of the houses were still under construction."

The multi-million-dollar homes went up in flames in the "Street of Dreams" development near Woodinville, in northwest Washington state.

Local media reported that the fire chief found signs with the initials of the Earth Liberation Front at the scene, and explosives were reportedly used to start the blaze.

Eastman declined to provide details about the suspected criminal origin of the fires, pending a statement by the county sheriff's office due later in the day.

Fox News reported that the FBI was investigating the fire as a "domestic terrorism act".

The loosely organized radical environmental group has been accused by US authorities of using terror tactics in several arson attacks in Western states to drive home their message on the damage being caused to the environment.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.