No one answered a phone listing for Singleton and it was not clear whether he had an attorney.
A Conway spokeswoman said that Singleton's clinic in Jeffersonville closed recently. The Indiana Medical Licensing Board voted last month to suspend the license of a doctor who worked at the clinic after a petition was filed citing unsafe prescribing practices.
No doctors were named in the indictment, but the Kentucky Board of Medical Licensure has taken disciplinary action against five physicians affiliated with the two Kentucky clinics that Singleton operated, the attorney general's office said.
Two of the doctors have agreed to indefinite practice restrictions and must pay $10,000 fines for violating the Medical Practice Act, the AG's office said. One physician remains suspended pending final action by the state regulatory board, it said.
Associated Press writer Roger Alford in Frankfort, Ky., contributed to this report.