The US Department of Justice is reportedly investigating several major pharmaceutical manufacturers and distributors for their role in propagating the opioid crisis.

Earlier this week, the Wall Street Journal reported that Johnson & Johnson, Teva, McKesson, Mallinckrodt, AmerisourceBergen, and Amneal Pharmaceuticals have all received grand-jury subpoenas from the US Attorney’s Office in Brooklyn, New York. Federal prosecutors have not officially confirmed or denied that a full-blown criminal investigation is underway, but many of these companies have publicly admitted to receiving these subpoenas.

On Tuesday, Johnson & Johnson and its subsidiary company, Janssen, released a statement acknowledging that they had received a subpoena as part of a “broader, industry-wide investigation into manufacturers’ and distributors’ monitoring programs and reporting under the Controlled Substances Act,” according to the Associated Press.

The Justice Department has already investigated Purdue Pharma, makers of OxyContin, for allegedly failing to report doctors who were illegally prescribing their popular medicine. The company has also been sued by no less than 36 states for defrauding regulators and misleading the public about the addictive risks of their product. The company eventually filed for bankruptcy after reaching a tentative deal to settle nearly 2,000 lawsuits for around $10 billion.

All of the companies that have so far been named in the probe, with the exception of Amneal, are also defendants in another 2,000 civil lawsuits filed by state and local governments. Among other claims, these lawsuits argue that these companies violated the Controlled Substances Act by failing to report or stop suspicious drug orders and shipments.

Earlier this year, Oklahoma Attorney General Mike Hunter sued Johnson & Johnson, Purdue Pharma, and Teva Pharmaceutical for intentionally downplaying the addictive risks of their products in order to boost their sales. This summer, a judge found Johnson & Johnson guilty and demanded that the company pay Oklahoma $572 million in damages. Teva and Purdue settled out of court, for $85 million and $270 million respectively.

The US Centers for Disease Control and Prevention report that nearly 218,000 people died from prescription opioid overdoses between 1999 and 2017, and nearly 200,000 more died from overdosing on illegal opioids. The financial impact of this crisis has cost the country $631 billion in the last four years alone, according to a recent report.

Prosecutors are expected to continue to issue subpoenas in connection with the probe. This does not guarantee that the federal government will place criminal charges against any of these companies, but if they decide to do so, it may be the largest prosecution of Big Pharma ever to be seen in the US.