Two black boxes from the downed Malaysia Airlines jet are being sent to the United Kingdom for analysis, while the bodies of hundreds of victims arrived in the Ukraine government-held city of Kharkiv on Tuesday.

The Boeing 777’s black boxes — which are actually orange in colour — will travel directly from Ukraine to a lab under the Air Accidents Investigations Branch in Aldershot in southern England, Malaysia's deputy transport minister says.

"The procedure is to have the black boxes sent to the nearest lab that is authorized by the International Civil Aviation Organization for analysis," Aziz Kaprawi said.

A refrigerated train, meanwhile, travelled overnight from the rebel-controlled town of Torez near the crash site, where hundreds of bodies had been kept for several days, to Kharkiv, where the Ukrainian government has set up its own crash investigation centre.

International police agency Interpol said it has a team in Kharkiv that has begun identifying the bodies. 

"The remains of victims recovered so far were labelled and numbered," Interpol said in a statement.

"The Interpol Incident Response Team, along with other international disaster victim identification teams in place, will carry out preliminary examinations."

It said that once the preliminary examinations are completed the victims will be transported to the Netherlands where fuller identification will be carried out. 

All 298 passengers and crew aboard flight MH17 were killed when the plane went down, including 193 people from the Netherlands. It’s unclear how many bodies have been recovered.

Most likely shot down by mistake, U.S. source says

Senior U.S. intelligence officials said Tuesday they have no evidence of direct Russian government involvement in the shooting down of Malaysia Airlines Flight 17.

The sources, speaking to the Associated Press on condition of anonymity, said the passenger jet was likely felled by an SA-11 surface-to-air missile fired by Russian-backed separatists in eastern Ukraine and that Russia "created the conditions" for the downing by arming the separatists. A senior official said the most likely explanation for the downing of the plane was that it was shot down by mistake.

Dutch Prime Minister Mark Rutte said he expects the victims’ bodies to be flown to the Netherlands on Wednesday.

Rutte said the identification of some bodies will be quick. But he has warned grieving families of victims of Thursday's crash that the identification of some others could take "weeks or even months." 

Investigation begins at crash site

The CBC’s Susan Ormiston, reporting from the crash site, said three investigators from Malaysia Airlines have arrived and begun combing through the wreckage.

"We sometimes forget this is their plane, and this is their accident investigation," Ormiston said.

More aviation experts are expected to arrive in the coming days after pro-Russian rebels agreed to give them "safe access" to the site under a deal brokered with the Malaysian government.

There remain serious concerns, however, that the evidence has been tampered with as recently as last night. Many large pieces of debris, including the cockpit, appear to have been cut apart so bits could be removed, Ormiston said.

"This is a real laboratory of clues and evidence," she said.

But "this is not the crash scene it was last Thursday."

Crash site needs security: Australian PM

Australian Prime Minister Tony Abbott said Tuesday that countries that have been "so wronged" should take responsibility for securing the crime scene where the Malaysian jetliner was apparently shot down in Ukraine.

Abbott listed Malaysia, the Netherlands as well as Australia among countries affected by the incident.

But he did not say whether Australia, which lost 37 citizens and residents, would be prepared to send troops or police to secure the site for independent investigators, saying the security arrangements were still under discussion among government leaders.

"There does need to be security for the site and I would think that security for the site would best be provided by the countries that have been so wronged here," Abbott told reporters.

"There's quite a long way to go between what we've got now and what we would like to see, which is a fully secure and protected site where investigators can go about their task without hindrance from others," he said.

The UN Security Council unanimously backed an Australian-drafted resolution on Monday demanding that pro-Russian rebels controlling the crash site refrain from compromising evidence, but Abbott said the site continued to be trampled.

"After the crime, comes the cover-up. What we have seen is evidence tampering on an industrial scale and obviously that has to stop," Abbott said.

Red Cross deems Ukraine conflict is a war

The  International Committee of the Red Cross (ICRC) has made a confidential legal assessment that Ukraine is officially in a war, Western diplomats and officials say, opening the door to possible war crimes prosecutions, including over the downing of MH17.

"Clearly it's an international conflict and therefore this is most probably a war crime," one Western diplomat in Geneva told Reuters.

The ICRC is the guardian of the Geneva Conventions that lay out the rules of war, and as such is considered a reference in the United Nations deciding when violence has evolved into an armed conflict.

UKRAINE-CRISIS/TRAIN

While international investigators have reached the crash site of Malaysia Airlines Flight MH17, world leaders and diplomats continue to make the case that the site should be secured by international forces. (Maxim ZMeyev/Reuters)

The ICRC has not made any public statement — seeking not to offend either Ukraine or Russia by calling it a civil war or a case of foreign aggression — but it has done so privately and informed the parties to the conflict, sources told Reuters.

"The qualification has been shared bilaterally and confidentially," ICRC spokeswoman Anastasia Isyuk told Reuters on Friday. "We do not discuss it publicly."

The designation as a war — either international or civil — changes the game legally, because it turns both sides into combatants with equal liability for war crimes, which have no statute of limitations and cannot be absolved by an amnesty.

Suspects may also be arrested abroad, since some countries apply "universal jurisdiction" to war crimes.

Dutch prosecutors opened an investigation into the MH17 crash on suspicion of murder, war crimes and intentionally downing an airliner on Monday.

With files from CBC News and The Associated Press