Congressional officials are warning car owners to beware of scams playing off the Cash for Clunkers program.

They say some fraudulent Web sites ask consumers for personal information to register. But registering is not necessary for Cash for Clunkers. That paperwork is taken care of at the dealership when you go to buy or lease a new car.

The Cash for Clunkers program gives consumers up to $4,500 in federal subsidies if they trade in their cars for new, more energy-efficient models. The cars must meet certain criteria for owners to qualify.