Flight MH17 was brought down by shrapnel that caused “massive explosive decompression,” analysis of the black box recorders has found.
The results, given today by Ukrainian security official Andriy Lysenko, have, however, left Dutch officials stunned as they did not expect the "premature" announcement.
Mr Lysenko told a news conference that the fragments had come from a rocket blast.
His source however, is under scrutiny after the Dutch Safety Board (DSB) confirmed they did not give the information to Ukraine.
DSB spokeswoman Sara Vernooij told The Independent: "I can’t make a comment on what source Mr. Lysenko has.
"We don’t want to confirm or say anything about the information on the black boxes right now; this in the best interest of the investigation itself.
"We want to analyse [and] combine information of several sources before we bring out anything, so we can give a coherent view on the whole investigation.
"Bringing out fragmented pieces of information is not on behalf of the investigation."
The board, which is leading the investigation, had been expected to release its initial findings on 1 August.
It did not question the veracity of Mr Lysenko's claims but suggested that the early release of the information was not in the interest of the investigation.
Britain's Air Accidents Investigation Branch (AAIB) was tasked with retrieving important data from the recovered flight recorders.
It comes as a senior UN diplomat claims that the downing of MH17 could “amount to a war crime.”
Navi Pillay, the UN High Commissioner for Human Rights today called for an immediate and wide-ranging investigation into the shooting down of the Malaysian Airlines passenger plane.
The Kuala Lumpur-bound flight crashed in eastern Ukraine on rebel-held territory amid incessant violence and wrangling between pro-Russian militants and Ukrainian troops.
It is thought that the Boeing 777 was shot down on 17 July by a surface-to-air missile, though a full investigation has yet to get underway.
“This violation of international law, given the prevailing circumstances, may amount to a war crime,” Ms Pillay said.
Some western countries including Ukraine blame rebels for the MH17 crash, in addition to Russia for allegedly supplying militants with arms, while separatists and Russian President Vladimir Putin deny the allegations, blaming Ukrainian military jets.
“It is imperative that a prompt, thorough, effective, independent and impartial investigation be conducted into this event,” Ms Pillay added.
Dutch and Australian experts, who were on their way to the crash location in eastern Ukraine, have had their fresh attempt to reach the site thwarted after intense fighting rendered the mission too dangerous.
The international experts had secured assurances from separatist leader Alexander Borodai that they would be able to conduct a full investigation on the shattered remains of MH17, as well as recover the bodies that still haven't been found.
However, their mission was halted both yesterday and today due to heavy fighting between rebel militants and government troops, as Ukraine attempts to claw back some of the separatist-held land.
Dutch Prime Minister Mark Rutte rejected the idea of deploying armed guards to help investigators secure the site as it could "destabilise" a situation which is already volatile.
Russia is continuing to deny involvement in the crisis, following US Secretary of State John Kerry's plea for the country to stop providing weaponry to Ukrainian rebels.
Washington said it was not accepting Russian foreign minister Sergei Lavrov's denial that it is not contributing to the violence.
Over the weekend, Russia accused the US of being behind "an unrelenting campaign of slander against Russia, ever more relying on open lies."
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