LOS ANGELES - SpaceX engineers are investigating the cause of Saturday's failed flight of the Falcon 1, a low-cost, light-lift rocket developed by the Southern California-based company.

SpaceX CEO Elon Musk says in a news release that a problem occurred causing the rocket's two stages to remain together instead of separating after the launch from a Central Pacific atoll.

However, he described the launch, powered by the company's new Merlin engine, as "picture perfect."

SpaceX is developing the single-engine Falcon 1, the nine-engine Falcon 9, the 27-engine Heavy Falcon and the Dragon cargo-crew capsule to fly to the International Space Station when the current space shuttle fleet retires in 2010.