OAKLAND, Calif. - It might start with a sawing noise or people pulling up to your parked car. Before you know it, thieves have taken off with your catalytic converter.
"It probably takes these guys once they know what they're doing maybe 10 minutes to cut a catalytic converter out. And then they're gone," said German Lara, who owns Lafayette German Car Repair.
And that means a normally quiet car like a Prius might suddenly make a loud noise.
"I'm trying to drive out in the morning, and there's this awful sound," said Amitava Ghose of Oakland.
Ghose owns two Priuses. Thieves stole a converter from one of them.
"It's ridiculous," Ghose said. "The whole thing is kind of like out of control here."
Out of control, because thieves are out to get rich: the converters, which control exhaust emissions, contain palladium and rhodium, metals that are now more valuable than gold.
"Mostly on Toyota Priuses, Honda Elements, Ford pickup trucks and now Land Rovers," said Chris Sullivan, who owns the Smog Shop in San Francisco.
Mechanics say they are awash in repair requests.
"Increasing our volume, and just call volume for stolen converters probably by about 30 percent - a day," Sullivan said
A replacement converter can cost several thousand dollars. Mechanics can also install plates or cages to help thwart thieves.
One Prius owner put a sign up on the car - with the word "warning" in three languages - saying the converter underneath has been welded.
Police have made arrests. The California Highway Patrol chased a BMW from San Francisco to Oakland, where it plunged off the freeway. In the trunk were stolen converters.
But going after the metal recylers can be a challenge.
"Like most other things, if there's a market for it, there's going to be a black market of people who are going to pay for it," Lara said.
Police say thieves often sell converters far from where they steal them, making it all hard to track.
"It is pretty rare for a criminal to decide they're going to tell us basically who their cash source is," said Santa Rosa police Sgt. Christopher Mahurin. "They're not going to want to give that information up."