Sao Paulo, Brazil ? Autopsies have revealed fractures in the legs, hips and arms of Air France disaster victims, injuries that — along with the large pieces of wreckage pulled from the Atlantic — strongly suggest the plane broke up in the air, experts said Wednesday.

With more than 400 bits of debris recovered from the ocean’s surface, the top French investigator expressed optimism about discovering what brought down Flight 447, but he also called the conditions — far from land in very deep waters — “one of the worst situations ever known in an accident investigation.”

French investigators are beginning to form “an image that is progressively less fuzzy,” Paul-Louis Arslanian, who runs the French air accident investigation agency BEA, told a news conference outside Paris.

A spokesman for Brazilian medical examiners told The Associated Press on Wednesday that fractures were found in autopsies on an undisclosed number of the 50 bodies recovered so far. The official spoke on condition he not be named due to department rules.