The BBC reports:
Alexander Borodai said the devices had been taken to Donetsk, the biggest rebel-held city in the east.
NBC adds that there is confusion about the identity of the men seen carrying the black boxes (which are actually orange for visibility purposes):
It is not clear what happened to the black box. The crash site, in a contested area of eastern Ukraine, is under the control of pro-Russian separatists. The men in the video are wearing Ukrainian Emergency Ministry uniforms, but a senior Ukrainian official told a news conference Sunday that rebels had taken the black boxes. Andriy Lysenko, spokesman for the Ukrainian National Security and Defense Council, said the search of the site was being complicated by the rebels. Bodies of some of the victims were seized at gunpoint by rebels and stored on a train. However, the militants' leader told NBC News the bodies were removed by rebels who were being "humane."
Both the government in Kiev and the separatist leaders appear to agree, however, that the separatists have the flight data recorders, though the separatist deny that they have moved the black boxes to Moscow.
Here is the video: