Dutch prosecutors on Wednesday charged Russians Igor Girkin, Sergey Dubinsky and Oleg Pulatov and Ukrainian Leonie Kharachenko with murder over the July 17, 2014 disaster that left 298 people dead, including 38 Australians.

The crash probe's Joint Investigation Team admits those men - who are allegedly responsible for bringing the missile launcher into the area - are only the middle of the chain of command.

Australian Federal Police Detective Superintendent David Nelson says the JIT still wants to prosecute those who pulled the trigger and those who gave the order.

They are also going after the Russian military officials who allowed the weapon to be moved over the international border, he said.

"We had a call for witnesses today focused on the members of the 53rd brigade that could provide some insight with the crew of the (missile launcher) Buk-TELAR," Det Supt Nelson told AAP.

"But also others were involved in the hierarchy that may have provided the orders and the authority for that weapon be taken into eastern Ukraine."

One person who could provide answers is an unnamed Russian army captain, who was the lieutenant in charge of the 3rd Battalion of the Russian 53rd Anti-aircraft Missile Brigade, which deployed the missile launcher to the Ukraine.

"That individual is one of a number of people that could give us a greater insight into what happened in that particular event on the 17th of July (2014), but also the identity of the crew," Det Supt Nelson said.

He explained that finding out who gave the order and who pulled the trigger will also determine if the missile was fired accidentally or deliberately, which he said there was still speculation about.

The four charged on Wednesday will be tried - likely in absentia - in The Hague, the Netherlands, on March 9.

Australian Associated Press