Relatives of victims killed in the downing of a Malaysia Airlines jet over Ukraine more than two years ago are gathering to learn the preliminary results of a Dutch-led criminal probe.

The team that conducted the largest investigation in Dutch history is scheduled to brief victims' families behind closed doors on Wednesday morning.

Investigators will hold a news conference later in the day to make their findings public.

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Thomas Schansman, father of the only US citizen killed in the July 2014 disaster - which claimed 298 lives, said he expects investigators to identify which specific weapon they believe destroyed flight MH17, and where it was fired from.

He said family members do not expect investigators at this stage to name the people they believe were responsible.

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A separate investigation by Dutch safety officials last year found the Amsterdam-to-Kuala Lumpur flight was downed by a Buk missile fired from territory held by pro-Russian rebels.