When you think of thieves stealing stuff from your car, you could probably imagine your sound system or other high-tech gear as the target of choice. However, criminals are now interested in whats on the underside of your car instead of whats in it. Ruston Barrowes SUV is driving fine, but just weeks ago it was a different story. I started it up and it was really loud. It really startled me," said Barrowes. Jason Brown had the same problem when he turned his car on one day recently. It sounded like I started a semitruck," said Brown. The catalytic converters in both cars were stolen right from the underbelly of the cars. Barrowes said, I never would have imagined that somebody would steal that." I was really surprised that it was stolen," said Brown. AAA said drivers should not be surprised because this particular part is now a hot commodity for car thieves. We really have seen a widespread problem with catalytic converter thefts. They're simply cutting the catalytic converters right out of the exhaust system and taking them and reselling them, said John Nielsen of AAA. The devices are required by the Environmental Protection Agency to help filter out harmful emissions. To do that, the device uses metals that are extremely valuable like platinum, rhodium and palladium. Some may contain even a 10th of an ounce of these metals and they're very profitable to resell," said Nielsen. The National Insurance Crime Bureau said thieves sell the devices to unknowing scrap recyclers who remove the metals. It is such a big problem that the Institute of Scrap Recycling Industries is taking steps to put the brakes on the crime. We have told our members that anyone who brings in a catalytic converter who you don't know already to be either an auto dismantler or the owner of an auto repair shop should be at least a little suspicious," said Chuck Carr of the Institute of Scrap Recycling Industries. How will you know if your converter is stolen from your car? You'll know it as soon as you start it up," said Nielsen. Brown said, It sounded like one of those really loud motorcycles." If that happens, experts said it is critical that you do not drive your car. The exhaust is very hot. It could be to the point where it actually starts to melt wires and cables and hoses, and it could damage very expensive components of your car. It could start a fire," said Carr. Replacing a converter could run anywhere from $200 to more than $1,000, and that could go much higher if other parts of your car are damaged during a theft. They can cause structural damage maybe to the frame of the vehicle or the floor board," said Frank Scafidi of the National Insurance Crime Bureau. There was no structural damage on Barrowes or Browns cars, but they did have to foot the bill for their new converters since their insurance deductible did not cover costs. I was pretty angry when this happened," said Barrowes. Experts said there is little drivers could do to protect their cars from catalytic converter thefts, but they recommended always parking cars in a well-list area and to never leave a car overnight in an area that is not secure.