(Reuters) - The U.S. Justice Department on Thursday announced charges against 412 people for taking part in healthcare frauds and opioid-related crimes that cost taxpayers about $1.3 billion.

The arrests came as part of what the department said was the largest healthcare fraud takedown in U.S. history. Those arrested included 120 doctors and other people charged for their roles in prescribing and distributing opioid painkillers.

The defendants include six doctors in Michigan accused of operating a scheme to prescribe patients with unnecessary opioids and of billing the Medicare healthcare program for $164 million in fraudulent claims.

Another case involved a fake Florida rehab clinic that recruited addicts with gift cards, visits to strip clubs and even drugs, resulting in $58 million in false treatments and tests, prosecutors said.

U.S. Attorney General Jeff Sessions said in Washington that the takedown highlighted the “enormity of the fraud challenge we face.

“This problem is compounded by the fact that our country is in the midst of the deadliest drug crisis in our history,” Sessions added.

Opioids, including prescription painkillers and heroin, killed more than 33,000 people in the United States in 2015, according to the U.S. Centers for Disease Control and Prevention.

Sessions said the charges against the 120 people for opioid-related crimes made the crackdown the biggest of its kind in U.S. history.

He said that too many doctors, nurses and pharmacists had chosen to put profit ahead of their patients, in some cases turning their practices into “multimillion-dollar criminal enterprises.

“They seem oblivious to the disastrous consequences of their greed,” he said. “Their actions not only enrich themselves often at the expense of taxpayers but also feed addictions and cause addictions to start.”

Of the 412 people charged nationally, 56 were doctors, the Justice Department said. It said that a result of the operation, 295 healthcare providers were in the process of being suspended or banned from participating in federal health programs.