Pro-Russian rebels are restricting access to the crash site of MH17, and may even have destroyed evidence linked to the attack, reports suggest.
A standoff at the wreckage between investigators from the Organisation for Security and Cooperation in Europe (OSCE) and rebels reportedly led to a warning shot being fired.
The fate of black boxes and other devices recovered from the plane are also unknown.
Despite calls for a full and independent probe into the disaster which claimed the lives of 298 people, the OSCE said armed personnel prevented observers inspecting the wreckage fully.
"We encountered armed personnel who acted in a very impolite and unprofessional manner. Some of them even looked slightly intoxicated," a spokesman added.
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.
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