The Building Industry Association of Washington, the state's homebuilders lobby, yesterday offered a $100,000 reward for information leading to the arrest and conviction of Earth Liberation Front (ELF) members suspected of arsons and attempted arsons in Washington state.

The FBI has linked ELF, a loosely knit group that has taken aim at what it regards as "urban sprawl," to four arsons and attempted arsons in Western Washington over the past 18 months. Those include the torching of two homes under construction in Snohomish County in April 2004.

In some cases, ELF claimed responsibility for the crimes, the FBI said.

"ELF's increasingly brazen attacks on urban targets have BIAW and the FBI worried that it is only a matter of time before someone is hurt or killed by ELF terrorists," said BIAW President Lyle Fox. In Washington alone, ELF members have been responsible for nearly $8 million in property damage since 1996, he said.

Appearing at a news conference with Fox, Laura Laughlin, FBI special agent in charge of the Seattle office, said such "special-interest extremism" linked to ELF and the Animal Liberation Front (ALF), has emerged as a serious domestic-terrorist threat.

The FBI released the following list of arsons and attempted arsons that targeted new housing construction in Washington in the past 18 months:

• April 10, 2004: Two homes under construction in Snohomish County were destroyed. A total of 13 incendiary devices were found at three different housing developments nearby. ELF claimed responsibility in a note left at the scene.

• July 6, 2004: A sign advertising lots for sale at a home-construction site near Bellingham was burned. ELF claimed responsibility.

• March 3, 2005: Two incendiary devices were found at a housing-construction site in Redmond. There was no claim of responsibility, but the devices were similar to those ELF previously used.

• April 13, 2005: Someone tried to burn down a home under construction in Sammamish but an incendiary device didn't ignite. ELF claimed responsibility on a large banner at the scene.