 Pathologists were uncertain whether the presence of the gas in the bodies could have been a result of decomposition that had occurred after the crash.Investigators concluded that one probable source of the gas was an unexpected failure in one of the engines, such as one that released all or part of one of the propellers or turbocharger disks into the fuselage.Such a failure could have easily caused a fire, disabled the radios, and caused serious flight control difficulties.