An old problem has returned to a part of the Bronx: the theft of cars, and an especially expensive auto part. NY1's Dean Meminger filed the following report.

On the quiet streets of the northeast Bronx, car thieves are hard at work. 

"If you are riding around and you see someone underneath a car, that should raise some red flags," said Inspector Ruel Stephenson, commander of the 47th Precinct.

At a community meeting, the 47th Precinct commander warned residents to be on the lookout.

So far this year, at least 78 vehicles have been stolen in the area patrolled by the 47th Precinct. That's a 53 percent increase from the same time period last year.

But car parts are being snatched as well, including expensive catalytic converters that reduce harmful emissions. 

"You have teams of two or three individuals who can easily slide underneath these vehicles and with some sort of mechanical tool, remove it," Stephenson said.

Police say it's a crime pattern happening across the Bronx.

Mechanic Roberto Vazquez says he has replaced converters for many upset car owners.

"I parked my car with no noise, and all of a sudden, I turn it on and it sounds like a truck," Vazquez said.

Often the part is sold to scrap metal yards or used car part shops. If sold for scrap metal, a catalytic converter would get about $50.  But if you needed to buy a new one for your car, that would be $600. Some converters cost more than $1,000.

A scrap metal yard in the 47th Precinct does a big business buying and selling converters. Workers say anyone who sells them converters and other parts must provide a driver's license, which is then kept on file, an effort to deter thieves.

The police are keeping an eye on the shops around the Bronx.

"Checking their logs, checking individuals who are frequent customers there. And we ourselves have tested trying to sell items to these shops," Stephenson said.

Ethaine Vassell says he had other items stolen in the middle of the day.

"Everything is in the seats. Doors were open," Vassell said. "They stole, like, my GPS."

Police are encouraging people to call 911 if they see anything suspicious as they try to put the brakes on the car thieves.