(CNN) — The Justice Department on Monday filed a lawsuit against Rite Aid for allegedly violating the Controlled Substances Act, alleging that the company “knowingly filled unlawful prescriptions for controlled substances.”

In a statement, Attorney General Merrick Garland said the Department of Justice is “using every tool at our disposal” to hold Rite Aid accountable for contributing to the opioid epidemic.

Associate Attorney General Vanita Gupta said “Rite Aid’s pharmacists repeatedly filled prescriptions for controlled substances with obvious red flags, and Rite Aid intentionally deleted internal notes about suspicious prescribers. These practices opened the floodgates for millions of opioid pills and other controlled substances to flow illegally out of Rite Aid’s stores.”

In the complaint, The Justice department alleges that from May 2014 to June 2019, Rite Aid filled thousands of unlawful combinations of prescriptions known as “the trinity” which included prescriptions for “excessive quantities of opioids, such as oxycodone and fentanyl.”

Rite Aid pharmacists were accused of ignoring obvious signs of misuse and intentionally deleting some pharmacists’ internal warnings about suspicious prescribers, such as “cash only pill mill???”

“These practices opened the floodgates for millions of opioid pills and other controlled substances to flow illegally out of Rite Aid’s stores,” Associate Attorney General Vanita Gupta said.

The Justice Department said the prescriptions, who were issued illegally, “lacked a legitimate medical purpose, were not for a medically accepted indication, or were not issued in the usual course of professional practice.”

Rite Aid is one of the country’s largest pharmacy chains, with more than 2,330 stores in 17 US states. It did not immediately respond to requests for comment.

The Justice Department accused Rite Aid of violating the federal False Claims Act by submitting false prescription claims to government health care programs such as Medicare and Medicaid.

It joined a whistleblower lawsuit filed in 2019 by two pharmacists and a pharmacy technician from Rite Aid stores in Pennsylvania, North Carolina and West Virginia.

The Justice Department occasionally joins whistleblower cases it considers stronger.

It has also sued Walmart and drug distributor AmerisourceBergen Corp over their alleged roles in the nation’s opioid crisis.

More than 500,000 people died from drug overdoses in the United States from 1999 to 2020, including more than 90,000 in 2020 alone, according to the US Centers for Disease Control and Prevention.

Reuters contributed to this report.

US sues Rite Aid for missing opioid red flags