Carrie Fisher's autopsy has been completed, revealing uncertainty over her how she died.

The death certificate of actress Carrie Fisher has been issued, however, it does not yet specify a cause of death.

Most famous for her role in Star Wars, 60-year-old Fisher passed away at 8:55am on December 27, after suffering a “cardiac episode” on a flight from London to Los Angeles four days prior.

CPR was performed by passengers onboard the United Airlines flight, TMZ reported, after her heart stopped 15 minutes prior to landing in Los Angeles.

The situation was said to be so desperate that she did not have a pulse for several minutes.

Fisher was then rushed to UCLA Medical Centre following the 11-hour flight, and was said to be in "a lot of distress".

On December 26, Carrie's mother Debbie Reynolds tweeted "Carrie is in a stable condition".

Carrie is in stable condition.If there is a change,we will share it. For all her fans & friends. I thank you for your prayers & good wishes. pic.twitter.com/isXJqqFEB6

— Debbie Reynolds (@DebbieReynolds1) December 25, 2016

Although the circumstances surrounding her death are known, the cause itself is unclear.

After an autopsy performed by the L.A. County Coroner's Office, it was found that the cause of death is "not obvious" and was decided that a conclusion would be "deferred".

A death certificate was required in order for the family to organise her funeral. The coroner will need to do further tests to determine what ended Fisher's life.

Fisher's mother, Debbie Reynolds, died a day after her daughter on December 28, at 84 years old. The pair will have a joint funeral, and be buried alongside each other at the Hollywood Hills' Forest Lawn Memorial Park.

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Todd Fisher, Reynolds' only son, told The Associated Press that his mother's last words were "I want to be with Carrie", and only moments later she was gone.

"My mother and my sister are together right now," he said. "She didn't die of a broken heart. She just left to be with Carrie."

The funeral will be private, and no date has yet been set. There are also been unconfirmed reports of a public memorial.