Investigators want to talk to the driver of a blue van that firefighters saw leaving a housing development where dozens of homes under construction burned, authorities said Wednesday.

Arson has been ruled the cause at least seven of the fires, and although the investigators do not know if the van was involved, they want to speak with the driver, said Capt. Joe Montminy of the Charles County sheriff's office.

"Obviously, that person is a potential witness, but possibly something more," Montminy said.

Authorities don't know how many people were in the van, why it was there, or if it had any connection to the fires Monday, Montminy said. The blazes in the Hunters Brooke (search) development, about 25 miles south of Washington, destroyed 12 homes and damaged 14. Just one of the damaged homes was occupied, and the family has been displaced while the investigation continues.

The development had been criticized by environmentalists, and investigators have not ruled out ecoterrorism, or any other motive, such as race. Many of the new homeowners in Hunters Brooke are black, but Montminy said the area is racially mixed.

On Tuesday, FBI (search) spokesman Barry Maddox said the agency was not aware of any claims of credit by any group. Maddox also said he was not aware of any recent activity in the Washington area by radical environmental groups such as the Earth Liberation Front (search).

Charles County has experienced rapid growth in recent years as the Washington suburbs spread outward from the city, causing disputes over where and how to build.

The Sierra Club (search) called the Hunters Brooke development "quintessential sprawl," saying it is far from existing infrastructure and "threatens a fragile wetland and important historical sites near the Chesapeake Bay."

After the fires, the group issued a statement saying it "strongly condemns all acts of violence in the name of the environment."