HRABOVE, Ukraine (AP) -- International monitors moved gingerly Saturday through fields reeking of the decomposing corpses that fell from a Malaysian airliner shot down over rebel-held eastern Ukraine, trying to secure the sprawling site in hopes that a credible investigation can be conducted.
But before inspectors ever reach the scene, doubts arose about whether evidence was being compromised.
The Ukrainian government and separatist rebels accuse each other of firing a surface-to-air missile at the Boeing 777 with almost 300 people aboard. Many see the hand of Russia, either for its suspected support of the insurgents or perhaps for firing the missile itself.
The latest U.S. intelligence assessment suggests that more than one missile system was provided to the separatists by the Russians in the last week or so, a U.S. official said Saturday.
While there is not 100 percent certainty, the official told The Associated Press, "more and more there is the general belief that the systems were provided by the Russians."
The official said it's not entirely clear if the separatists just received the missile systems or if they had them for a short time and only in recent days were trained or able to operate them. The official was not authorized to discuss the matter publicly and spoke on condition of anonymity.
The government in Kiev said militiamen had removed 38 bodies from the crash site near the Russian border and taken them to the rebel-held city of Donetsk. It said the remains were transported with help from specialists with distinct Russian accents.
The rebels are also "seeking large transports to carry away plane fragments to Russia," the Ukrainian government said Saturday.
In Donetsk, separatist leader Alexander Borodai denied that any bodies had been transferred or that the rebels had in any way interfered with the work of observers. He said he encouraged the involvement of the international community in assisting with the cleanup before the bodies deteriorate further.
Ukraine called on Moscow to insist that the pro-Russia rebels grant international experts the ability to conduct a thorough, impartial investigation into the downing of the plane, echoing a demand that President Barack Obama issued a day earlier from Washington.
The jet flying from Amsterdam to Kuala Lumpur carried 298 passengers and crew from 13 countries. More than half were Dutch.
On Saturday, in the village of Hrabove, one body was seen still strapped into an airline seat, with bare toes peeking out under long jeans. Another body was flung face-up into a field of blue flowers.
Treatment of the victims' remains, left in the open air under a hot summer sun punctuated by bursts of rain, provoked outrage and distress.
"The news we got today of the bodies being dragged around, of the site not being treated properly, has really created a shock in the Netherlands," Dutch Foreign Minister Frans Timmermans told the Ukrainian president in Kiev. "People are angry, are furious at what they hear."
Timmermans demanded the culprits be found.
"Once we have the proof, we will not stop until the people are brought to justice," he said.
An angry Dutch prime minister told reporters Saturday that he was "shocked by images of completely disrespectful behavior" of rebels picking through the wreckage and personal belongings of victims at the crash scene. Mark Rutte said he had an "extremely intense" telephone conversation with Russian President Vladimir Putin in which he urged Putin to "show the world he intends to help" in the investigation.
The U.S. State Department said it was deeply concerned that the separatists' had refused to allow monitors safe and unfettered access to the crash site. Spokeswoman Jen Psaki said the monitors were allowed 75 minutes at the site Friday and less than three hours Saturday. She said noted e reports about bodies being removed, debris taken away, and potential evidence tampered with.
"This is unacceptable and an affront to all those who lost loved ones and to the dignity the victims deserve," Psaki said in a statement.
Putin and German Chancellor Angela Merkel agreed Saturday in a phone call that an independent commission led by the International Civil Aviation Organization should be granted swift access to the crash site, according to the German government and the Kremlin.
The commission should examine the circumstances of the crash and recover the victims, German government spokesman Georg Streiter said.
Russia has "a key role to play" through its influence on the separatists, "and the world's eyes will be on Russia to see that she delivers on her obligations," British Foreign Secretary Philip Hammond said.