"The underlying cause of death is the condition which starts the downhill course of events leading to death and in this case is the immersion associated with drug intoxication," a release on a Brown's death said.
The information was released on what would have been Brown's birthday; the only child of Whitney Houston and Bobby Brown died at a hospice facility at age 22, months after she was discovered in the tub.
"The autopsy alone could not reveal the underlying cause of death because of the long interval between Ms. Brown being found unresponsive in the bathtub and her eventual death," the medical examiner's release states. "Thus, the underlying cause of death is based substantially on review of medical records, the results of toxicology tests, investigative records, and the fact that the autopsy did not show any other likely underlying cause of death or reason for Ms. Brown becoming unresponsive."
Earlier this week, a judge ruled that Brown's autopsy records could be unsealed, siding with media organizations that had been seeking the information, the Associated Press reported.
Bobbi Kristina's death bears similarities to her mother's; Whitney Houston was discovered face-down in a bathtub at the Beverly Hilton hotel in February 2012. She died at age 48.
Marijuana and alcohol were among the substances cited in Friday's statement, as well as medications that were used "for sedation or to treat anxiety."
Officials also investigated the manner of Brown's death, which means they looked at whether it occurred because of natural causes or an intentional act, or whether an unintentional cause was to blame. However, the release states, that wasn't something authorities could figure out.
"Death was clearly not due to natural causes, but the medical examiner has not been able to determine whether death was due to intentional or accidental causes, and has therefore classified the manner of death as Undetermined," the release states.