Fake doctor prescribed massive opioid dosages at Texas 'pill mill': Feds Arif was accused of conspiring with the owner of Aster Medical Clinic.

A Texas man was found guilty Wednesday of posing as a physician at an illegal pain clinic that federal authorities described as a "pill mill."

A jury found Muhammad Arif, 61, of Katy, Texas, guilty of one count of conspiracy to unlawfully distribute and dispense controlled substances, and three counts of unlawfully distributing and dispensing controlled substances, the Department of Justice said.

Arif was accused of conspiring with the owner of Aster Medical Clinic, an unregistered pain clinic in Rosenburg, Texas, where prosecutors said workers illegally prescribed "hundreds of thousands of doses" of opioids and other controlled substances, according to a statement.

Arif allegedly wrote prescriptions for patients on pads that had been pre-signed by a doctor, who was also named as a co-conspirator in the case.

Clinic employees allegedly brought people to pose as patients and paid for their visits in order to obtain prescriptions for controlled substances that so-called crew leaders would then sell on the street.

Aster Medical Clinic charged about $250 for each patient visit, and required payment in cash, prosecutors said. The clinic would serve more than 40 people on its busiest days.

"Through this scheme, Aster Medical Clinic dispensed prescriptions for over 200,000 dosage units of hydrocodone, a Schedule II controlled substance, and over 145,000 dosage units of carisoprodol, a Schedule IV controlled substance," the DOJ said in a statement. "The combination of hydrocodone and carisoprodol is a dangerous drug cocktail with no known medical benefit, the evidence showed."

Two co-conspirators have pleaded guilty based on their roles in the scheme and are currently awaiting sentencing, according to the DOJ.

Arif is expected to be sentenced at a later date.

ABC News' Pierre Thomas contributed to this report.