The U.S. Department of Agriculture (USDA) is looking to crack down on welfare fraud around the country.

The USDA’s Food and Nutrition Service announced Wednesday it is targeting people who sell food stamps for money. Some recipients cheat the system by claiming they have lost their food stamp debit cards so they can request new ones, the agency said. 

To combat fraud, the USDA will require states to monitor the Supplemental Nutrition Assistance Program and be on the lookout for excessive requests for replacement cards. People who request four or more replacements in a year will receive a warning notice.

“If trafficking is suspected, the state agency must refer the cases to the state’s fraud investigation unit,” the USDA wrote in the Federal Register.

“After the fourth replacement card, a household’s shopping behavior is three times more likely to be flagged as potential trafficking,” the agency added.

The Supplemental Nutrition Assistance Program is the nation’s largest food assistance program for low-income people. It used to provide food stamps to people, but now it deposits those food stamps on electronic cards, which act like debit cards that recipients can use to buy groceries.

In 2013, the entitlement program cost taxpayers $76.4 billion, supplying more than 47 million low-income people with an average of $133 a month to buy food.

But the program is susceptible to fraud. In an effort to crack down on people who sell their cards, the USDA published an interim rule that required states to monitor card replacement activity. 

Since then, states have cut down on the fraud, the agency noted. Now, 8 out of 10 recipients do not request any replacement cards, and 98 percent request three or fewer cards each year.

“Based on current data, the number of clients requesting five or more cards has decreased nationally since many states adopted this practice,” the USDA said.

The USDA is finalizing the rule effective immediately.