Marty Boyer's carefully maintained sport utility vehicle growled more like a dragster than a 2001 Honda Passport when he turned the key.

"The second I turned it over, and it sounded like a tank and a Harley, I knew exactly what had occurred," said Boyer, 33, .

A half-dozen office colleagues had told him about that roar after their own catalytic converters were stolen, a crime that has been rising rapidly across the country from riverside parking lots in Cincinnati to highways along the California coast.

The pollution-reducing converters contain small amounts of the precious metals platinum and palladium, and they've joined copper wire and sewer grates on the long list of metal items targeted by thieves eager to cash in on climbing metal commodity prices.

Converter thieves slip under vehicles with battery-powered saws, sometimes in daylight, and in a matter of minutes leave owners with shocking repair bills.

The thefts were only a sporadic problem nationally until about a year ago but have grown to a near-epidemic, said Frank Scafidi, a spokesman for the National Insurance Crime Bureau. Scafidi received an overwhelming response when he recently questioned bureau agents.

"Everybody was seeing reports of this, hearing reports of this, talking to the local cops _ all over the country," he said.

Since January, 43 converter thefts were reported in downtown Cincinnati, compared with eight during the first half of 2007, said police Lt. Mark Briede.

In Arizona, the Phoenix police department's metal thefts squad has grown to accommodate a rash of thefts, including converters. Authorities in Portland, Ore. and Memphis, Tenn., also report increases.

California has become a hot spot, especially in the Sacramento and San Francisco areas, and thieves sometimes steal vehicles and abandon them after removing the converters, said Lt. Chris Costigan of the California Highway Patrol.

No comprehensive national totals are available on converter thefts, which are usually lumped into theft or vandalism categories.

Converters have been standard equipment since the mid-1970s, and some newer vehicles have up to four.

Five years ago, platinum traded for about $608 per troy ounce and palladium went for $208. Platinum now goes for $2,083 per troy ounce, and palladium draws about $468 on the New York Mercantile Exchange. A troy ounce is a a metal measurement slightly larger than a common ounce.

Prices have increased with demand as use of catalytic converters grew and platinum jewelry gained in popularity, said Larry Manziek, executive director of the International Precious Metals Institute, a Pensacola, Fla.-based trade organization. In the last year, electronic trading of platinum also increased, making the metal an easier investment, he said.

Scrap yards usually pay $50 to $100 per converter, but industry experts say the price varies among buyers, said Bruce Savage, a spokesman for the Institute of Scrap Recycling Industries, a trade organization.

Converter replacement costs are much higher, ranging from about $200 for a universal model to $1,000 or more for one from the vehicle manufacturer.

Boyer, an assistant technology director at a downtown business, paid $572 to replace his and plans to spend $360 for converter protectors. He's now so wary that he put off buying a new vehicle and instead started driving an older car to work.

For car owners willing to spend extra, there are products such as the CatClamp, a tough-to-cut converter cage sold by American Welders Inc. of Toledo, starting around $225. For others, police say the best defense is a watchful eye, a bit of luck and increased awareness among law enforcement.

Cincinnati auto repair shop owner Randy Rice empathizes. He fixes damaged exhaust systems _ one came in with the saw still inside _ and he's even had to replace 10 converters stolen from cars on his lot, at his own expense. Now he's adding a new security camera and extra lighting.

Across the Ohio River in Newport and Covington, Ky., officials tightened regulations for scrap yards, requiring that they copy the driver's license of anyone trying to sell metal. Covington yards also hold metal for a month to allow stolen items to be reclaimed.

That follows the advice of the scrap yard trade group, which urges its 1,600 members to document each transaction, making it easier for police to follow up. The organization also forwards theft alerts from law enforcement agencies to its members.

Boyer says there's no easy solution.

"I could teach my 6-year-old how to do it in probably 15 minutes," he said. "It's like stealing from somebody while their windows are down."

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On the Net:

Institute of Scrap Recycling Industries: http://www.isri.org/

National Insurance Crime Bureau: http://www.nicb.org/