The cause of Carrie Fisher's has been confirmed as a cardiac arrest, but officials say more investigation is needed to determine the underlying cause.

The Los Angeles County Department of Public Health issued the death certificate for the star on Tuesday, listing the cause of death as "cardiac arrest/ deferred".

This indicates that more investigation is needed by the county coroner, usually in the form of toxicology tests that can take several weeks to complete.

Listed as the notifying party is the actress and writer's daughter Billie Lourd.

The death certificate lists Fisher's occupation as a writer, since it was as a novelist that she spent most her life.


Image: Carrie Fisher and mother Debbie Reynolds had a joint memorial service

But it was for her role as Princess Leia in the Star Wars franchise that she was best known for.

Fisher had been promoting her latest book, The Princess Diarist, when she suffered a cardiac arrest on a flight from London to Los Angeles.

She died four days later, aged 60, at the Ronald Reagan UCLA Medical Center.

Her mother, actress Debbie Reynolds, died the following day.

The two actresses had a joint, private memorial service last week.

Fisher's ashes were carried to the funeral by her brother inside a giant Prozac pill urn.