Further investigation is needed to determine the underlying cause of Carrie Fisher's heart attack, according to her death certificate.
The Los Angeles County Department of Public Health issued the death certificate, obtained by The Associated Press, in the name of Carrie Frances Fisher.
Under "cause of death" it says "cardiac arrest/deferred". The "deferred" designation indicates that more investigation is needed by the county coroner, usually in the form of toxicology tests that can take several weeks to complete.
Fisher's daughter, Billie Lourd, is listed as the notifying party.
The Star Wars actress had the heart attack on a flight from London to Los Angeles on December 23. She died at age 60 on December 27 at Ronald Reagan UCLA Medical Center, the certificate says.
Her mother, Singin' In The Rain star Debbie Reynolds, died the following day at another Los Angeles hospital, after having her own medical emergency while making memorial plans for her daughter.
The death certificate lists "writer" as the occupation in which Fisher spent most of her life.
It also says Fisher had been in the entertainment business for 46 years and her highest level of education was 10th grade.
The information in the certificate was first reported by TMZ.
Fisher and her mother were mourned in a joint memorial at their neighbouring homes on Thursday and had a joint funeral at a Hollywood Hills cemetery the next day.
Relatives have said they are planning a public memorial for them.