A federal agency in charge of travel safety said Sunday preliminary findings of a probe into the engine that exploded last week revealed two fan blades were fractured. A Pratt & Whitney PW4077 engine on a United Airlines-owned Boing 777-200 exploded shortly after the plane took off Saturday from Denver International Airport. Pilots were able to maneuver the flight to safety with no injuries or deaths, but the sudden detonation has caused widespread concern and immediately triggered an investigation. The National Transportation Safety Board said that early findings show the Pratt & Whitney had two fractured fan blades. One was fractured near the root and an adjacent blade was fractured about mid-span. A portion of one blade was embedded in the containment ring. The remainder of the blades were damaged at the tips and leading edges. In addition, the inlet and cowling, which covers the engine, were separated from the engine. Despite …