Two doctors have pleaded not guilty to federal charges of illegally prescribing narcotic prescription drugs and Medicaid fraud.

Kachen Clement Yeung and Barry N. Odegaard were indicted in separate cases by a federal grand jury last week after an investigation that included undercover Drug Enforcement Administration agents posing as patients.

The indictments were unsealed after the two were arrested Monday. They pleaded not guilty on Monday.

U.S. Magistrate Judge Leslie Kobayashi scheduled the trials for June 6.

Both were permitted to be free on bond and can still practice medicine, but they had to surrender their DEA certificates permitting them to prescribe controlled drugs, Assistant U.S. Attorney Thomas Muelheck said.

Yeung and Odegaard were both accused of prescribing a pain killer "outside the course of professional medical practice and not for a legitimate medical purpose." Muelheck said the drug was OxyContin, the trade name for Oxycodone.

The doctors were paid in cash by the undercover agents, but the physicians also submitted claims to Medicaid, essentially "double billing," Muelheck said.

Yeung was indicted on 30 counts of illegal prescriptions and 19 counts of Medicaid fraud. Odegaard was charged with 10 illegal prescription counts and five Medicaid fraud counts.

The prescription charges each carry up to 20 years in prison. The Medicaid fraud counts each carry up to 10 years in prison.