The coroner said the complete toxicology report remained sealed at the request of the Los Angeles police and the Los Angeles county district attorney.
The Los Angeles police department said its investigation was continuing but that police were referring the case to prosecutors for possible criminal charges.
Propofol is a powerful anesthetic used to induce unconsciousness in patients undergoing major surgery in hospital.
Medical professionals say it should never be used by private individuals at home.
Jackson is to be buried at a cemetery in Glendale, California, on September 3.