Updated at 3:40 p.m. ET

The Justice Department filed a lawsuit against Walmart on Tuesday, alleging that the retail giant unlawfully dispensed controlled substances from pharmacies it operated nationwide.

The government says that, between the actions of the company's pharmacies and its distribution centers, Walmart helped to fuel America's ongoing opioid crisis.Damages in the civil case could total in the billions of dollars, the Justice Department said.

"As one of the largest pharmacy chains and wholesale drug distributors in the country, Walmart had the responsibility and the means to help prevent the diversion of prescription opioids," Jeffrey Bossert Clark, acting assistant attorney general of the Civil Division, said in a statement.

"Instead, for years, it did the opposite — filling thousands of invalid prescriptions at its pharmacies and failing to report suspicious orders of opioids and other drugs placed by those pharmacies," he added. "This unlawful conduct contributed to the epidemic of opioid abuse throughout the United States. Today's filing represents an important step in the effort to hold Walmart accountable for such conduct."

If the retailer is found liable in the case, it could face civil penalties of up to $67,627 for each unlawful prescription filled and $15,691 for each suspicious order not reported.

The case, which the department says was the result of a multi-year investigation, was filed in federal court in Delaware.

The complaint alleges that Walmart violated the Controlled Substances Act in multiple ways, as the operator of both pharmacies and wholesale drug distribution centers.

At its pharmacies, Walmart is alleged to have knowingly filled thousands of controlled substance prescriptions that were not issued for legitimate medical purposes. And at its distribution centers, the government says Walmart received hundreds of thousands of suspicious orders that it failed to report to the Drug Enforcement Administration, as required.

In a statement on Tuesday, Walmart defended itself against the allegations – and said the DEA itself was to blame.

"The Justice Department's investigation is tainted by historical ethics violations, and this lawsuit invents a legal theory that unlawfully forces pharmacists to come between patients and their doctors, and is riddled with factual inaccuracies and cherry-picked documents taken out of context. Blaming pharmacists for not second-guessing the very doctors DEA approved to prescribe opioids is a transparent attempt to shift blame from DEA's well-documented failures in keeping bad doctors from prescribing opioids in the first place," it said.

Walmart says it had "always empowered" pharmacists to refuse to fill problematic opioids prescriptions, which it said they did hundreds of thousands of times. The company says it sent thousands of investigative leads to the DEA, and blocked thousands of questionable doctors from having their opioid prescriptions filled at its pharmacies.

The retailer, which is headquartered in Bentonville, Ark., had a total revenue last year of $524 billion.

Robert Higdon Jr., U.S. Attorney for the Eastern District of North Carolina, said in a statement that his own district has been devastated by addiction and abuse – and that Walmart only made things worse.

"For example, our office prosecuted a physician for illegal opioid distribution," Higdon said. "A jury convicted him just last year, and he is currently serving a twenty-year prison sentence. As it turns out, that physician expressly directed patients to Walmart to have their opioid prescriptions filled. Walmart's own pharmacists reported concerns about the doctor up the corporate chain, but for years, Walmart did nothing—except continue to dispense thousands of opioid pills."

In October, under the threat of the now-announced lawsuit, Walmart sued the Justice Department and the DEA, asking a federal court to clarify the roles and responsibilities of pharmacists and pharmacies under the Controlled Substances Act. The case is pending in federal court in the Eastern District of Texas.

Copyright 2021 NPR. To see more, visit https://www.npr.org.