Massachusetts and federal welfare officials are teaming up with local police departments to target stores that illegally traffic in Supplemental Nutrition Assistance Program, or SNAP, benefits.

Until now, local police have been limited to investigating welfare recipients suspected of fraud.

Under the agreement signed Monday, police will also be able to investigate stores for fraud. That fraud can involve using cash to purchase welfare benefits from recipients for half their face value.

In the last fiscal year, 22 stores in Massachusetts were permanently disqualified from the SNAP program because of fraud.

So far, four police departments have signed onto the agreement, including those in Everett, Taunton, Attleboro and Pittsfield.

The federal SNAP program was formerly known as food stamps.

The agreement follows reports earlier this year that pointed to fraud in public benefits programs.