The complaint also says CVS sought reimbursement from federal health care programs for such prescriptions in violation of the False Claims Act. CVS is the largest pharmacy chain in the U.S., where there are more than 9,000 pharmacies.

A representative of CVS said the company has cooperated with the DOJ’s investigation for more than four years, and strongly disagrees with the allegations and what it called the “false narrative” within the complaint.

Among the unlawful prescriptions that CVS allegedly filled from Oct. 17, 2013, to the present were for dangerous and excessive quantities of opioids, early fills of opioids, and “trinity” prescriptions — a dangerous combination of drugs made up of an opioid, a benzodiazepine and a muscle relaxant, according to prosecutors.

CVS also allegedly filled large quantities of prescriptions for controlled substances written by prescribers it knew to be engaged in “pill mill practices” — that is, prescribers who issue large numbers of controlled substance prescriptions without any medical purpose, investigators said.

According to the complaint, CVS ignored substantial evidence from multiple sources, including its own pharmacists and internal data, indicating that its stores were dispensing such prescriptions.

“This lawsuit alleges that CVS failed to exercise its critical role as gatekeeper of dangerous prescription opioids and, instead, facilitated the illegal proliferation of these highly addictive drugs, including by pill mill prescribers,” U.S. Attorney Zachary Cunha for the District of Rhode Island said in a press release.

If CVS is found liable, it could face civil penalties for each unlawful prescription filled and treble damages and other penalties for each prescription reimbursed by federal health care programs.

The company said it’s cooperated with investigators.

“We will defend ourselves vigorously against this misguided federal lawsuit, which follows on the heels of years of litigation over these issues by state and local governments — claims that already have been largely resolved by a global agreement with the participating state Attorneys General,” said Amy Thibault, director of external communications for CVS in a written statement.

Each of the prescriptions in question was for an FDA-approved opioid medication prescribed by a practitioner who the government itself licensed, authorized and empowered to write controlled-substance prescriptions, Thibault added.

The filing of the complaint follows the announcement on Friday that the McKinsey & Company consulting firm has agreed to pay $650 million to settle a federal investigation into its work to help opioids manufacturer Purdue Pharma boost the sales of the highly addictive drug OxyContin.

It’s the latest effort by federal prosecutors to hold companies accountable that officials say helped fuel the U.S. addiction and overdose crisis, with opioids linked to more than 80,000 annual deaths in some recent years. For the past decade, most of these deaths have mostly been attributed to illicit fentanyl, which is laced into many illegal drugs. Earlier in the epidemic, prescription pills were the primary cause of death.

Over the past eight years, drugmakers, wholesalers and pharmacies have agreed to about $50 billion worth of settlements with governments — with most of the money required to be used to fight the crisis.