US officials have started to investigate why a Virgin Galactic space rocket crashed over California’s Mojave desert on a test flight.

One pilot died and the other was badly injured when SpaceShipTwo exploded shortly after take-off on Friday.

A National Transportation Safety Board team arrived in Mojave on Saturday and was heading to the crash site.

Virgin chief Sir Richard Branson said he was “determined to find out what went wrong” and learn from the tragedy.

The dead pilot was named as Michael Alsbury, aged 39. The pilot who survived Friday’s crash has not been identified.