The Dutch Safety Board, which is leading an international inquiry into the downing of Malaysia Airlines flight MH17, said on Wednesday (local time) investigators had found no evidence that the jet's "black box" voice recorder had been tampered with.
The DSB also said it expected to get the information it needs from the crash site in eastern Ukraine, although much evidence had been damaged or lost.
Experts have been downloading data from the Boeing 777's voice and data recorders at Britain's Air Accidents Investigation Branch after pro-Russian rebels, who control the crash sites in eastern Ukraine, handed them over early on Tuesday.
"The Cockpit Voice Recorder was damaged but the part that contains the data was intact," the DSB said in a statement. "Nor was there any evidence or indication that (it) had been manipulated."
Rebels released the recorders more than four days after the disaster in which 298 people, two thirds of whom were Dutch citizens, died. Ukraine has accused the rebels of tampering with the recorders, while the United States has said its suspects they shot down the jet with a Russian-made missile.
"Despite the fact that evidence and traces have been damaged or lost, the DSB expects it will be able to gather sufficient relevant information from the crash site," the DSB said.
It added that it would coordinate a team of 24 investigators from Ukraine, Malaysia, Germany, the United States, Britain and Russia, as well as the International Civil Aviation Organisation.