BOSTON – CVS Pharmacy has agreed to pay $3.5 million to settle allegations that dozens of its Massachusetts pharmacies violated federal law by filling forged prescriptions for addictive painkillers and other controlled substances.

U.S. Attorney Carmen Ortiz announced the settlement with the Woonsocket, Rhode Island-based drugstore chain Thursday.

CVS says it entered into the agreement to avoid the expense and uncertainty of further legal proceedings.

Ortiz’s office says the settlement resolves two investigations by the Drug Enforcement Administration after reports of forged oxycodone prescriptions. One involved hundreds of forged prescriptions at 40 CVS stores in Massachusetts and New Hampshire. The other involved 120 forged prescriptions at 10 CVS stores in and around Boston.

CVS says it has tightened its policies and procedures to help its pharmacists determine whether a prescription is legitimate.