Four days after Whitney Houston's death, her doctors' drug records were subpoenaed by the Los Angeles County coroner's office.

The coroner told the Associated Press Wednesday that investigators have contacted doctors in search of information about how the singer got prescription drugs that may have contributed to her death Saturday at the age of 48.

We've already contacted a number of doctors with requests for records, Assistant Chief Coroner Ed Winter told the Associated Press. Winter said such a move is common in these sorts of deaths.

Subpoena power is one of the wonderful tools an investigator uses to get information from pharmacies and doctors, Dave Campbell, a retired captain from the coroner's office, said. You're primarily seeking documents, not the persons who treated or prescribed, because you are doing a death investigation, not a criminal investigation.

Several bottles of prescription drugs were found by authorities in Whitney Houston's room at the Beverly Hilton hotel in Beverly Hills, Calif., where her dead body was pulled from a bathtub Saturday afternoon.

Toxicology tests on Houston's body have not been completed yet, and authorities say it could be eight weeks until they are ready to be released.

Defense attorney Ellyn Garofalo, who secured an acquittal in the case of a doctor accused of over-prescribing drugs to Anna Nicole Smith, told the Los Angeles Times that investigators will likely look at the amount of drugs gathered in the Beverly Hilton room, the amount she was prescribed, the doctors who prescribed the, and the pharmacies that dispensed the medications.

Whitney Houston, one of history's all-time best-selling musicians, was pronounced dead on Saturday at 3:55 p.m. PT. The newest news reports indicate that the singer likely died of a combination of drugs and alcohol. Initially, her cause of death was rumored to be drowning, as the singer was found in the bathtub of her hotel room. However, there was reportedly not enough water in the tub for the singer to drown.

Houston's last meal included room-service, champagne and Heineken. Empty medicine bottles were found her hotel room, along with pills like Xanax and ibuprofen.

Whitney Houston's private funeral is slated to take place Saturday in her hometown of Newark, N.J., at the New Hope Baptist Church, where Houston began her singing career at a young age. The funeral, which is invite-only, is being handled by Newark's Whigham Funeral Home, which also tended to the funeral affairs of Whitney Houston's father, John Houston.