42 CFR § 455.15 - Full investigation.
If the findings of a preliminary investigation give the agency reason to believe that an incident of fraud or abuse has occurred in the Medicaid program, the agency must take the following action, as appropriate:
(a) If a provider is suspected of fraud or abuse, the agency must—
(1) In States with a State Medicaid fraud control unit certified under subpart C of part 1002 of this title, refer the case to the unit under the terms of its agreement with the unit entered into under § 1002.309 of this title; or
(2) In States with no certified Medicaid fraud control unit, or in cases where no referral to the State Medicaid fraud control unit is required under paragraph (a)(1) of this section, conduct a full investigation or refer the case to the appropriate law enforcement agency.
(b) If there is reason to believe that a beneficiary has defrauded the Medicaid program, the agency must refer the case to an appropriate law enforcement agency.
(c) If there is reason to believe that a beneficiary has abused the Medicaid program, the agency must conduct a full investigation of the abuse.