A Massachusetts man pleaded guilty Monday for his role in an organized theft crew that stole hundreds of catalytic converters amid legal crackdowns and decreasing rates of catalytic converter thefts nationwide, prosecutors said.

Carlos Fonseca, 33, of Springfield, Massachusetts, pleaded guilty Monday to conspiracy to transport stolen property in interstate commerce and interstate transportation of stolen property, the U.S. Attorney's Office for the District of Massachusetts said in a news release Tuesday. Fonseca and six others were arrested and charged last April in connection to a string of catalytic converter thefts.

Between 2022 and 2023, the group transported and sold catalytic converters taken from at least 496 vehicles across Massachusetts and New Hampshire, prosecutors announced. Authorities estimated the group is responsible for $2 million in losses in the two states.

"It is believed that a significant number of additional thefts have not been identified or were not ever reported to law enforcement," according to the U.S. Attorney's Office.

Fonseca's guilty plea comes amid a nationwide crackdown on catalytic converter thefts, which skyrocketed during the COVID-19 pandemic. But recent data showed a decline in thefts last year, which public data company BeenVerified contributed to falling prices of precious metals found in catalytic converters.

The data company noted that federal and state efforts, including catalytic converter crime ring busts and tighter legal restrictions, could be working as well. Over 40 states have strengthened restrictions on scrap recyclers and penalties, such as prison time and fines, since 2021, according to BeenVerified.

Catalytic converter thefts fell after Massachusetts takedown in 2023

Fonseca was a member of an organized theft crew that used battery-operated power tools and car jacks to steal catalytic converters from vehicles in Massachusetts and New Hampshire, the U.S. Attorney's Office said. The group used an internet application that provided real-time prices for catalytic converters and targeted specific vehicle models to maximize their profits.

"The theft crew would travel hundreds of miles, hours on end in a single night, to specific locations, including home driveways and business parking lots where large numbers of these vehicles were located," the U.S. Attorney's Office added. "On numerous occasions, the crew targeted more than 10 vehicles in a single night, with one night resulting in thefts from 26 vehicles."

Fonseca participated in catalytic converter thefts from more than 100 vehicles in 13 separate instances between Aug. 23, 2022 and Oct. 4, 2022, according to the U.S. Attorney's Office. The thefts resulted in losses of about $5,000 for each vehicle and certain trucks cost over $10,000 to repair.

More than 300 victims had been targeted by the group, including businesses and individuals, the U.S. Attorney's Office said. After stealing the catalytic converters, the group would sell them to an individual who sold them to scrap dealers for about approximately $30,000 to $80,000 per week.

Since members of the group were arrested and charged last April, prosecutors said there has been a decline in catalytic converter thefts reported in Massachusetts. The U.S. Attorney's Office said only seven catalytic converter thefts have been reported over the past 11 months, compared to the hundreds of thefts reported the nine months before the arrests.

Catalytic converter theft a 'nationwide problem'

Catalytic converter theft has become a "nationwide problem across the country," according to the U.S. Attorney's Office. Catalytic converters are part of a vehicle’s exhaust device and its core contains valuable precious metals that can be removed in minutes.

Some metals found in catalytic converters are more valuable than gold and the black-market price can be more than $1,000 each, the U.S. Attorney's Office said.

Catalytic converters also often lack identifying markings, making it difficult to track down. And vehicles become inoperable – both mechanically and legally under Environmental Protection Agency regulations – after catalytic converters are removed.

Between 2019 and 2020, catalytic converter thefts increased by 325%, according to the National Insurance Crime Bureau (NICB). Thefts surged and broke records in 2022.

The NICB said insurance claims for thefts increased from 16,660 in 2020 to 64,701 in 2022. "Catalytic converter theft claims had an upward trend trajectory throughout 2020 and 2021 and theft claims in 2022 were significantly higher than in previous years," according to the NICB.

Thefts significantly decreased in 2023

Although catalytic converter thefts are still higher than in 2019, vehicle data provider Bumper said thefts nationwide saw a steep decline in 2023. In the first 10 months of 2023, Bumper said there were 33,457 catalytic converter thefts, compared to 85,430 recorded in 2022.

The data provider also noted that more law enforcement and tighter state regulations may have contributed to the decline in thefts. In recent years, there have been numerous federal and state takedowns against crime rings and individuals for their role in stealing catalytic converters.

Contributing: Jessica Guynn and Celina Tebor, USA TODAY