The county coroner's office is investigating the Nov. 12 death, which was reported by the Los Angeles Police Department as a possible suicide, Lt. Ed Winter of the coroner's Investigations Bureau said Thursday.
The coroner performed an autopsy but the cause of death will not be announced until the results of blood and toxicology tests are returned. The investigation could take as long as four to six weeks.
Police said a friend of Brandis called 911 from the actor's apartment just before midnight on Nov. 11 to report Brandis had attempted suicide. Paramedics transported Brandis to Cedars-Sinai Medical Center, but he died the next day, police Detective Gene Parshall said.
The office of Brandis' agent at Innovative Artists refused to comment.
Brandis started his career in commercials and on television, landing a recurring role on the soap "One Life to Live" at age six. After moving with his family to Los Angeles at age nine, he made guest appearances on such shows as "L.A. Law," "Who's the Boss?" and "Murder, She Wrote."
Other film credits included the Rodney Dangerfield comedy "Ladybugs," and the martial arts comedy "Sidekicks" with Chuck Norris, and a small part in the 2002 film "Hart's War," starring Bruce Willis.
Brandis also starred as crew member Lucas Wolenczek in the underwater sci-fi series "SeaQuest DSV," a role that garnered him a Young Artists Award in 1993 and helped turn him into a teen idol.