A senior separatist leader, Aleksander Borodai, handed over black boxes from an airliner downed over eastern Ukraine to Malaysian experts in the city of Donetsk.
According to Reuters, both sides then signed a document, which Borodai said was a protocol to finalise the procedure.
Christopher Miller, editor at Kyiv Post, has posted a picture of the reported handover.
Thousands of online users have taken to social media to call for the victims of the Malaysian airliner crash to be returned to loved ones.
United States intelligence officials admitted that they do not know who fired the surface-to-air missile that downed flight MH17.
Warning this article contains images that some may find distressing