 Some of the material bore evidence of fire damage, and CAB investigators determined that the burns had occurred on the portions that had floated on the surface of the water; each piece had a definite waterline below which burn marks were not found.Investigators found no evidence of an in-flight fire, and laboratory tests of the charred pieces did not find any traces of prohibited or explosive material.In their investigation, CAB officials considered the hazardous materials that were known to be in the cargo hold of the flight.