California Department of Justice started the investigation of the death of the former Playboy Playmate Anna Nicole Smith.
The person, who spoke on condition of anonymity because the investigation was ongoing, declined to elaborate. California Attorney General Jerry Brown was expected to make an announcement later Friday.
Anna Nicole died of an accidental drug overdose in February at a Florida hotel. She was 39.
Several people close to the model have fallen under suspicion since her death, including her psychiatrist Dr. Khristine Eroshevich.
The Medical Board of California said in April it was investigating Eroshevich, who, according to documents, authorized all 11 prescription medications found in Smith's hotel room the day she died.
Eroshevich had traveled with Smith to Florida.
More than 600 pills, including 450 muscle relaxants, were missing from prescriptions that were no more than five weeks old, according to the documents, which were obtained by The Associated Press through a public records request.