(Reuters) - Fifty-eight people have been charged with engaging in healthcare fraud schemes that centered on the illegal distribution of more than 6 million opioid pills across Texas, U.S. prosecutors said on Wednesday.

Some 16 medical professionals, including six doctors and seven pharmacists, were charged in the schemes, which featured one pharmacy in Houston that illegally dispensed more than 760,000 pills from March 2018 to September 2019, Assistant Attorney General Brian Benczkowski told a news briefing in Dallas.

“The data in our possession shines an inescapable light on those dirty doctors, clinic owners, pharmacists and others who may have long believed that they could perpetrate their fraud in the dark, behind closed doors,” he said.

The opioid crisis has been marked by nearly 400,000 overdose deaths between 1999 and 2017, according to the latest U.S. data. About 218,000 of those deaths have been from prescription opioids, while the rest were from illicit opioids including heroin.

Some 45,000 people a year overdose on opioids in the United States, U.S. Attorney John Bash of the Western District of Texas said on Wednesday.

“The scale of this crisis is enormous,” he said.

The schemes in Texas entailed Medicare fraud that resulted in more than $66 million in losses, Benczkowski said. They also included $158 million in fraudulent claims for compound creams and $23 million in tax evasion, he said. Federal authorities have frozen $60 million in assets of the people accused, Benczkowski added.

“I hope today’s action brings home a simple message for those that engage in these despicable frauds,” he said. “You’re not invisible.”

The scheme in Houston involved counterfeit prescription pads associated with doctors whose identities were stolen. Runners would bring the prescriptions to the pharmacy to be filled on a cash-only basis while they charged more than five times the market rate for drugs such as oxycodone and hydrocodone, authorities said.

Separately, two doctors were charged with scheming to defraud TriCare, a healthcare program for U.S. military veterans, Benczkowski said.

The charges in Texas come after Purdue Pharma LP Purdue Pharma LP, which launched OxyContin in 1996, filed for bankruptcy protection on Sunday night, succumbing to pressure from more than 2,600 lawsuits alleging the company helped fuel the U.S. opioid epidemic.

Other criminal cases have been filed recently by state and federal authorities. Dozens of medical professionals in Appalachia were accused in April of writing hundreds of thousands of illegal prescriptions and committing health care fraud.