The investigation into the cause of a fatal gyrocopter crash late last week is underway and being led by officials of the Federal Aviation Administration. William Jenson of Hidden Valley Lake, the pilot, was pronounced dead at the scene. The cause of the crash has not yet been determined and is under investigation. Recovery of the aircraft proved difficult due to low tide, recovery was made with the help of an airboat. The aircraft was an experimental Gyrocopter Vortex, registered to an owner in Grass Valley.