LEWISTON — Police are warning residents to be on the lookout for catalytic converter thefts, after seeing a rise in reports.

Since the start of the year, a total of 16 thefts have been reported, seven in the past week alone, according to Lt. Derrick St. Laurent. In the past two years, an average of three to four catalytic converters have been reported stolen each month.

St. Laurent said the true number is likely higher. Some people may not have reported thefts to police and others haven’t yet realized they are victims.

Catalytic converters, which filter car exhaust, can be sold to scrap yards for $500 to $1,000, St. Laurent said.

“Catalytic converters contain expensive precious metals like platinum, palladium and rhodium,” according to a Facebook post by the Lewiston Police Department. “These recyclable materials can easily be ‘scrapped’ for quick profit.”

Residents realized their catalytic converters were stolen after their cars refused to start, St. Laurent said. There doesn’t appear to be any specific geographic area targeted, he added.

Neighboring municipalities, including Auburn, are also seeing more catalytic converter thefts than normal, he said.

Police are encouraging residents to park in well-lit areas where the vehicle is visible to cameras or members of the public. They are also asking the public to report suspicious activity around vehicles, such as someone working under a car.