A doctor has been arrested on charges of selling pain medication prescriptions out of his Triangle office for cash, an operation Prince William County police said put nearly 8,000 oxycodone pills a week on the street.

Alex Yadao, 73, who lives in the Alexandria section of Fairfax County, is accused of writing prescriptions for morphine, oxycodone and other pain medications to dozens of patients who didn’t need them, police said.

Three other people were arrested in the sting on Thursday, including two patients and Keith Edward Payne, 53, who lived in the basement of Yadao’s office on Old Triangle Road and allegedly helped sell the prescriptions.

Investigators observed people lined up outside Yadao’s office to buy prescriptions, according to a search warrant filed in Fairfax County court; several neighbors complained of patients in the area appearing to be under the influence of drugs.

“Yadao was selling prescriptions strictly to make money,” said Officer Jonathan Perok, a Prince William police spokesman. “That was the motive. It’s probably one of our biggest busts of a doctor writing false prescriptions.”

Perok said Yadao was selling thousands of dollars of prescriptions per week but declined to offer further details.

Prince William and Fairfax County police began investigating the general practitioner after a complaint of drug activity in the area, according to the warrant. Detectives set up surveillance on Yadao’s office in August, watching it into November.

At one point, investigators pulled over a patient who was driving a van recklessly after leaving Yadao’s office, according to the warrant. The patient told detectives that Yadao’s practice was “dirty” and that there were “a lot of drug addicts in and out.”

The man had received a prescription for a 30-day supply of oxycodone but could not explain the exact nature of his ailment to investigators, the warrant said. He has not been charged.

Yadao did not record the amount of drugs he was prescribing, never asked patients to take urine tests to see whether they were using the drugs and wrote prescriptions for people who did not have verified medical conditions that required the drugs, according to the search warrant.

In one instance, according to the warrant, he prescribed the same drug to the same person twice in five days.

Yadao is facing 36 counts related to charges of selling prescription drugs and writing false prescriptions. Payne is facing four drug-related charges. Both are being held without bond.

The men, along with a Fauquier County couple accused of being Yadao’s clients and charged with prescription fraud and possession of a controlled substance, are scheduled to appear in court in February.

Read more on PostLocal.com:

12 pedestrians hit, 2 killed in Montgomery County

D.C. police fatally shoot armed man in confrontation

Man killed in Reston shooting

Big change coming at Beltway/I-66 merge