Prosecutors in Indiana say more than two dozen people died as a result of illegal prescribing practices at a clinic in Kokomo, where a total of nine people have either been sentenced on or are still facing felony drug charges.

The latest doctor to be sentenced, William Terpstra, 67, pleaded guilty to dealing in a narcotic drug and dealing in a controlled substance.

Investigators claim Terpstra wrote more than 10,000 prescriptions for controlled substances in 2012.

According to police, doctors at the Wagoner Medical Centers in Burlington and Kokomo gave prescriptions to patients for narcotics, even after multiple failed drug screens. Such tests are given to patients in an effort to prevent the abuse of highly addictive, opiate-based drugs such as hydrocodone and oxycodone. If a patient tests negative for prescribed substances, doctors become concerned the patient either doesn’t need the medication, or might be giving away, stockpiling or selling the drug.

In this case, police say overprescription of painkillers, sedatives and other controlled substances by employees at the Wagoner clinics — including doctors Terpstra and fellow doctors Don Wagoner, Marilyn Wagoner and Robert Brewer — was responsible for a rash of overdose deaths, addicted patients and a flood of pills into the community.

In one instance, a patient told police the Wagoner clinic started requiring her to come in every week to be seen after she tested negative for the drug she’d been prescribed.

The patient said for seven straight weeks she would come in, test negative for the opiates she’d been prescribed, pay $332 in fees, and walk out with a seven-day supply of Lortab and Adderall, an often-abused drug used to treat attention deficit hyperactivity disorder.

Terpstra was one of nine people charged in the case, according to the Kokomo (Ind.) Tribune. He originally was charged with 24 counts in the case.

The clinic’s owner, Don Wagoner, 79, was the first to plead guilty in the case last year and thus far is the only one sentenced to prison time. With credit for time served, he was released in March and is currently serving eight years of in-home detention and 20 years of probation.

Following his 18-month in-home detention, Terpstra will serve the balance of his sentence on probation, a condition of which includes 100 hours of community service.

Terpstra’s license to practice medicine was also suspended for the rest of his life.

Thomas Hewitt and Gary Hartman, who were physician assistants at the clinic, and former nurse Linda Richards also have pleaded guilty and were sentenced to house arrest and probation.

Cases against former office manager Michelle Wagoner, 48, and Dr. Robert Brewer, 81, were both dismissed in August because they cooperated in the investigation, Howard County Deputy Prosecutor Ron Byal said.

Brewer faced two felony dealing in narcotic drug charges in the case and Michelle Wagoner faced three charges.

Two others charged in the case, Marilyn Wagoner, 78, and John Thomas, 67, have trials pending. Marilyn Wagoner’s trial is set for Oct. 23 and Thomas has a trial date of Nov. 13.

The Kokomo (Ind.) Tribune contributed to this story.