Already there is anecdotal evidence of flood-damaged vehicles turning up on lots in Florida, Arizona, New York and Oklahoma, authorities said. Two months ago, at least seven 2005 Nissans listed in the National Insurance Crime Bureau database as hurricane-damaged were sold at an auction in Los Angeles.

A task force of insurance investigators and Louisiana law enforcement officials is building a database of flooded cars to try to prevent vehicles from being spruced up and foisted upon unsuspecting used-car buyers. The database at http://www.nicb.org lists more than 205,000 vehicles...

Because there is a thriving market for stolen vehicles, autos are being handled differently from the rest of the debris. Identifying and tracking the hurricane-damaged vehicles not only prevents fraud but makes it easier for the vehicle's owner --- or the insurance company --- to recoup some of the vehicle's value by selling it to a rehabber or for scrap. An analysis by the consulting firm Towers Perrin estimated that insured losses from damaged automobiles ranged from $1 billion to $2 billion.

Experts warn that a car that has sat in saltwater is bound to have problems, even if it is repaired. Saltwater corrodes metal parts, gums up joints and damages electrical and computer systems, potentially ruining air bags, among other things. Another problem is that the water could leave behind traces of mold, chemicals or E. coli bacteria in the vehicle's interior.

"To me, the biggest concern about cars that are sitting in brackish water is air bags," said Lt. Allen Carpenter, head of the Louisiana State Police insurance fraud section. "You're dealing with a corroded sensor that may or may not work."