Structural failure rather than an engine explosion may have been responsible for Friday's crash of Virgin Galactic LLC's experimental space ship, safety experts said Sunday. The Wall Street Journal reported National Transportation Safety Board investigators said, however, it's too early to draw any conclusions.

The Journal said preliminary data point to a giant structural failure, but experts note some engine problems could sharply boost structural loads. NTSB Acting Chairman Christopher Hart it appeared Space Ship Two likely broke up in flight.

Space Ship Two debris A piece of debris is seen near the crash site of Virgin Galactic's SpaceShipTwo near Cantil, California Nov. 1, 2014. Photo: Reuters/Lucy Nicholson

Space Ship Two crashed Friday in the Southern California desert after separating from its carrier craft, WhiteKnightTwo. One of the two pilots aboard was killed. Virgin Galactic founder Richard Branson said he will continue to push forward with his space tourism program despite the crash.