Used car buyers should be wary of damp spots, musty smells and rust, all of which indicate that the vehicle may have flood damage, Jalopnik reported.

As many as 800,000 used cars on American roads may have been subject to "title washing," which is when vehicle documents are illegally altered to remove "salvage" or "flood" from a car's title, according to a Carfax press release.

The company, which runs reports on used vehicles for a fee, says that title washing is an "emerging fraud" that likely affects around 500 cars that are being used as taxis.

Con men take cars from states where they have been damaged by major storms and drive them elsewhere to sell them to deceived buyers.

Jalopnik listed some signs of flood damage that those in the used car market should watch for.

"If you see or feel any type of significant moisture or even dried mud on the seats, floors, glove compartment, tracks of the seat, or in the trunk, that car was most likely flooded," Jalopnik's Tom McParland wrote. "Also, look for moisture buildup or fog on the front and rear lights and the instrument panel."

Cars that have been flooded will retain a musty odor in the interior. Floors and upholstery should also be checked for stains since people who resell damaged cars will probably miss more difficult spots while cleaning them.

A New Jersey dealership was apparently selling vehicles that were damaged during Hurricane Sandy flooding. The dealer owner has admitted to selling flooded cars, while a state Department of Motor Vehicles employee confessed that he had been title washing the vehicles.

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