Kobe Bryant and his daughter Gianna were among the victims of a crash in California in January ©Getty Images

Blunt force trauma has been ruled as the official cause of death for the nine people on board a helicopter that crashed in January, included former Los Angeles Lakers and United States basketball player Kobe Bryant.

An autopsy report and the result of a toxicological test on the helicopter's pilot were both released yesterday, as reported by the Los Angeles Times.

The toxicological test on pilot Ara Zobayan did not detect either illegal substances or alcohol in the bloodstream.

The deaths of nine people, which included Bryant and his 13-year-old daughter Gianna, were declared accidental.

A federal investigation into the accident, which occurred on January 26 when the 1991 Sikorsky S-76B helicopter crashed into a hillside in Calabasas in California, continues.

A team of doctors from the Los Angeles County medical examiner-coroner's office conducted autopsies on the deceased.

The helicopter that was carrying Kobe and Gianna Bryant and seven other passengers was flying in conditions which included fog and low cloud ©LA County Sheriffs Office
The helicopter that was carrying Kobe and Gianna Bryant and seven other passengers was flying in conditions which included fog and low cloud ©LA County Sheriffs Office

The passengers who lost their lives in the crash included Orange Coast College baseball coach John Altobelli, 56, whose wife Keri, 46, and 14-year-old daughter Alyssa also died.

Other passengers on board were Christina Mauser, 38, an assistant coach selected by Bryant to work at his Mamba Sports Academy in Thousand Oaks, 13-year-old Payton Chester, a member at the academy and her mother Sarah, 45.

The helicopter was heading to the academy for a youth basketball game when it left John Wayne Airport at just after 9am on January 26.

According to a report from the National Transportation Safety Board, the helicopter was travelling in conditions including "fog and low clouds obscuring the hillside."

It narrowly missed hitting a previous hillside before the fatal crash.

In February, Kobe's wife Vanessa Bryant filed a wrongful death lawsuit against Island Express Holding Corp and Island Express Helicopter, which employed Zobayan.

In the lawsuit Zobayan was accused of several acts of negligence including failing to abort the flight, failing to monitor and assess the weather, and failure to keep a safe distance between natural obstacles and the helicopter.