TV AND WEB RESTRICTIONS~**DIGITAL USE ONLY, NO BROADCAST USE WORLDWIDE, NO ACCESS AUSTRALIA BROADCASTER WEBSITES. NO ACCESS JAPAN. NO ACCESS ABC AMERICA, FOX, UNIVISION, TELEMUNDO, BBC AMERICA, NBC, OR THEIR DIGITALMOBILE PLATFORMS. NO ACCESS LOS ANGELES, CALIFORNIA MEDIA MARKET WEBSITES.**br br As pieces of the Virgin Galactic SpaceShipTwo passenger ship lie scattered in California's Mojave Desert, the U.S. National Transportation Safety Board has started its investigation to find out what went wrong during Friday's test flight.br br A mid-air explosion brought down the air craft, killing one pilot and injuring the other.br br Acting NTSB Chairman Christopher Hart says there's a lot of potential evidence to sort through.br br (SOUNDBITE) (English) ACTING NTSB CHAIRMAN CHRISTOPHER HART SAYING:br br "This was a test flight and test flights are typically well documented in terms of data and we may get some video feeds.