An autopsy on the body of Christian Brando did not immediately determine what killed the son of the late actor Marlon Brando, authorities said Tuesday.

Christian Brando died Saturday at a Los Angeles hospital. The cause of death was listed as deferred, pending results of toxicology tests that may determine whether Brando had prescription or other drugs in his system and whether a medical condition was involved, Los Angeles County coroner’s official Ed Winter said.

Results should be available in six to eight weeks.

The autopsy was requested “based on his past drug history,” Los Angeles County coroner’s Lt. Fred Corral said Monday.

An attorney for Marlon Brando’s estate said the 49-year-old died of pneumonia.