The cause of death for all nine victims of the helicopter crash that killed Kobe Bryant and his daughter Gianna has been ruled as blunt trauma, a post-mortem has confirmed.

The Los Angeles County Department of Medical Examiner-coroner on Friday published the results from examinations of those who lost their lives in the incident in Calabasas, California on January 26.

The crash occurred amid heavy fog but an investigation into the cause is ongoing.

A statement read: "On January 28, the cause of death for all nine decedents was certified as blunt trauma. The manner of death was certified as accident."

Alyssa Altobelli, John Altobelli, Keri Altobelli, Payton Chester, Sarah Chester, Christina Mauser and pilot Ara Zobayan were on board with the Bryants.

A 180-page report also showed that Zobayan tested negative for drugs and alcohol.

Bryant was a five-time NBA champion during a 20-year career with the Los Angeles Lakers.

He was named the league's MVP in 2008, was selected for the All-Star Game on 18 occasions and received All-NBA First Team honours on 11 occasions.

The two-time Olympic gold medallist's jersey numbers of eight and 24 were retired by the Lakers following his death aged 41.