The stain of the nation’s opioid abuse and drug overdose crisis has spread now to Bentonville, Ark., as federal prosecutors have sued Walmart, accusing the nation’s largest retailer of improperly allowing its pharmacists to fill millions of suspicious prescriptions for potent painkillers.

The pharmacists themselves complained to their corporate bosses that they were delivering opioids in far too great quantities to too few customers in out-of-the-way places, prosecutors contend. The warnings were ignored.

Instead, Walmart operated too lax a system both to monitor its outlets’ dispensing of drugs and to provide legally required warning information to federal watchdogs about potentially problematic sales, the New York Times reported, quoting Jeffrey Bossert Clark, acting assistant attorney general of the U.S. Justice Department’s civil division: