Investigators work to determine cause of crash

US investigators are working to determine the causes of the helicopter crash that killed basketball star Kobe Bryant in California on Sunday.

All nine people on board the helicopter died, including Bryant's 13-year-old daughter, Gianna.

Investigators are expected to focus on the weather conditions, which were foggy, and on any mechanical failures that may have occurred.

Bryant was considered to be one of the greatest players in the game's history.

He was a five-time NBA champion for his only team, the Los Angeles Lakers, and a double Olympic gold medallist. He retired in April 2016.

Tributes from fans, fellow basketball players and other public figures have been pouring in from around the world.

Early on Monday morning, fans could be seen congregating at a makeshift memorial for the player in front of the Lakers' stadium at the Staples Center in Los Angeles. ‎

Italy has said a minute's silence would be observed at all basketball games "in every category for the entire week". Bryant spent part of his childhood in the country as his father played in the Italian basketball league.

Investigators from the Federal Aviation Administration (FAA) and the National Transportation Safety Board (NTSB) are gathering in the area to launch separate crash investigations, reports say.

The federal agency has a team of about 20 people in LA and will work with the FAA, the helicopters' manufacturer and the company that made its engine, the Washington Post reports.

Investigators began searching through the wreckage on Monday.