Federal agents arrested the founder of a major drug company in an early-morning raid Thursday on charges stemming from an alleged scheme to get doctors to illegally prescribe a powerful opioid to patients who don't need it.

John Kapoor, 74, was taken into custody in Phoenix, Arizona. Kapoor is the billionaire founder and former CEO of the pharmaceutical company Insys Therapeutics. He faces charges including racketeering, conspiracy, bribery and fraud.

John Kapoor, founder and former CEO of Insys Therapeutics Insys

Kapoor is the most significant pharmaceutical executive to be criminally charged in response to the nationwide opioid crisis.

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Brian Kelly, an attorney for Kapoor, said his client "is innocent of these charges and intends to fight the charges vigorously."

Kapoor stepped down as CEO of Insys in January but still serves on its board. The company makes a spray version of fentanyl, a highly addictive opioid intended only for cancer patients.

Authorities allege Insys marketed the drug as part of a scheme to get non-cancer doctors to prescribe it. Numerous physicians were allegedly paid bribes by the company to push the painkilling drug.

CBS News correspondent Jim Axelrod reports Insys made 18,000 payments to doctors in 2016 that totaled more than $2 million. CBS News has identified headache doctors, back pain specialists and even a psychiatrist who received thousands of dollars to promote the drug last year.

A federal judge on Thursday set bail for Kapoor at $1 million and ordered him to wear a electronic monitoring bracelet and to surrender his passport, CBS News' Pat Milton and Laura Strickler report.

Last December, six other Insys executives were indicted on federal charges in Boston in connection with the alleged scheme to bribe doctors to unnecessarily prescribe the painkilling drug.