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GRABOVE, Ukraine (CNN) — Twenty-seven more bodies have been found at the MH17 crash site in the Donetsk region of Ukraine, Vice Prime Minister Volodymyr Groysman said Sunday. That brings to 233 the total number of bodies recovered from the Malaysia Airlines passenger jet, which was shot down on Thursday.

Pro-Russia separatists are keeping the remains of 192 of those MH17 victims in refrigerated cars on a train, Groysman said, adding that talks are ongoing for their release.

The train was headed to the city of Donetsk, Russian state news agency RIA Novosti reported Sunday evening.

Meanwhile confusion is still rife over the state of the investigation into the crash of the downed plane, which killed all 298 people on board. Rebels are suspected of shooting down the plane with a Russian-made surface-to-air missile.

There were concerns the bodies had been picked over by thieves.

“The facts of looting, how the terrorists are dealing with the bodies, are beyond the moral boundaries,” Ukrainian President Petro Poroshenko tweeted.

The local head of the rebels denied responsibility when asked about people reportedly using stolen bank-issued cards taken from the victims’ bodies.

“It is possible that some local residents could have searched the bodies of victims, found their cards and tried to use them. Unfortunately, I can’t exclude the possibility of this,” Alexander Borodai said Saturday.

More order at crash site

The State Emergency Service said the search in the remote area of eastern Ukraine, roughly 40 kilometers (25 miles) from the Russian border, was being “complicated by armed separatists at the site who hinder the work of SES units.”

It said that hundreds of official staff members are taking part in the search for the remains of the MH17 victims, covering an area stretching across 34 square kilometers (13 square miles).

They were being helped by busloads of volunteers from local coal mines who fanned out across the wheat fields where the bodies and debris from the plane fell to earth Thursday.

The situation at the crash site showed some small signs of improvement, with more control and more activity. But it was still far from a well-organized investigation scene, and the area was still under the control of pro-Russia rebels.

Government emergency workers prevented vehicles from driving up the road to the main crash site, but people could still roam around the fields on foot.

U.S. Secretary of State John Kerry told CNN’s “State of the Union with Candy Crowley” that there were reports Sunday of “drunken separatists piling the remains of people into trucks in an unceremonious fashion.”

He said he spoke Saturday with Russian Foreign Minister Sergey Lavrov in what he called a “direct and tough conversation.”

Russia needs to help ensure that investigators can conduct a thorough investigation, he said.

Black boxes found?

Pro-Russia separatists may have recovered the plane’s flight data recorders, Borodai said Sunday on the website of the self-declared Donetsk People’s Republic. Borodai said if experts determine the devices found are the so-called black boxes, they would be turned over to international investigators.

“These are some technical objects. We cannot say for sure these are black boxes,” he said, according to a CNN translation.

Borodai said the devices are under guard in the region. They will not be given to Ukrainian officials, he said.

The Reuters news agency distributed video on Sunday of what appeared to be an inflight recorder found by a worker in a field in eastern Ukraine. The agency labeled the video, shot Friday, as showing one of the two flight data recorders from MH17.

Some Malaysian investigators flew to Kiev, the Ukrainian capital, on Saturday. But Malaysia’s official news agency Bernama said they were still negotiating with pro-Russian rebels over access for their team. On Sunday, the new agency said Malaysia was sending two large military cargo planes to bring back the remains of crash victims.

Law enforcement officials from the Netherlands, the United States and Australia have arrived or are being sent to Ukraine to work with the investigation, which is being led by the Ukrainian government in Kiev. Two FBI agents have arrived in Kiev, a senior U.S. law enforcement official told CNN. An investigator from the U.S. National Transportation Safety Board arrived Saturday.

Why that route?

On Saturday, a Malaysia Airlines executive explained why the Boeing 777 flew over Ukraine.

“We, along with hundreds of other airlines, have flown that route safely for quite some time,” said Hugh Dunleavy, commercial director for Malaysia Airlines. “Primarily we flew that route because we were advised that this was a safe corridor and there would be no incidents.”

Dunleavy said the flight adjusted its altitude while on its way across Europe under the direction of air traffic control.

He said the airline is reassessing the route it uses for the flight from Amsterdam to Kuala Lumpur.

Malaysia Airlines said Sunday that it will retire the flight number MH17 for the route, replacing it with the code MH19.

Families’ agonizing wait

For the families of the victims, the confusion at the scene of the crash deepens the suffering.

Silene Fredriks said her son and his girlfriend had taken Flight MH17 for a planned vacation in Bali. At Amsterdam’s Schiphol Airport on Sunday, she laid flowers and signed the condolence book.

She says she wants Russian President Vladimir Putin to ensure that the two young people’s remains make it back to the Netherlands.

“Mr. Putin must take care of my son and my daughter to bring them home,” she said. “I can do nothing but wait for their bodies.”

Pressure on Putin

Governments from around the world have expressed outrage at the disorderly situation at the crash site and called on Putin to use his influence on the pro-Russian rebels.

British Prime Minister David Cameron called Putin on Sunday to urge him to do what he can to ensure the victims “have proper funerals.”

Earlier Cameron wrote a Sunday Times opinion article urging Putin to find a way to make the crash site more accessible and calm the strife between Ukraine and the rebels.

“If President Putin does not change his approach to Ukraine, then Europe and the West must fundamentally change our approach to Russia,” Cameron wrote. Ten of the passengers on MH17, which was en route from Amsterdam to Kuala Lumpur, were British.

Australian Prime Minister Tony Abbott, whose country had 27 citizens on the plane, added to the pressure on Putin.

Describing the downing of the passenger jet as “a horrific crime,” Abbott said he had summoned Russian Trade Minister Denis Manturov, who is visiting Australia, and “made crystal clear my concerns and dissatisfaction with the way this has been handled.”

“Russian-controlled territory, Russian-backed rebels, quite likely a Russian-supplied weapon,” Abbott said in a television interview Sunday. “Russia can’t wash its hands of this.”

Finger-pointing

Since the crash, the Ukrainian government and pro-Russian rebels have traded bitter accusations over who was responsible and what has been done since.

Ukrainian officials have said that a Russian-made Buk M1 missile system, brought into eastern Ukraine from Russia, had shot down the Malaysian airliner.

The Ukrainian government has accused the rebels of removing debris and 38 bodies from the scene as part of an attempt to cover up what happened.

Borodai has rejected accusations that his forces shot down the plane, telling reporters that the rebels lacked the firepower to hit an aircraft that high.

Borodai also denied that his forces removed any bodies.

The United States has said evidence suggests a Russian-made surface-to-air missile fired from the rebel territory took down jet.

Kerry said a convoy of about 150 vehicles moved several weeks ago from Russia to eastern Ukraine. The military equipment included “multiple rocket launchers,” he said.

“It’s pretty clear that this is a system that was transferred from Russia in the hands of separatists,” Kerry told CNN on Sunday.

A written statement from the U.S. Embassy in Kiev also included mention of Russia providing training to separatists at a facility in southwest Russia.

“This effort included training on air defense systems,” the statement said.

U.S. officials believe the missile systems may have been moved back across the border into Russia, CNN foreign affairs reporter Elise Labott said Saturday.

Russia has denied any involvement, and Putin said Ukraine’s military campaign against the rebels was to blame. He also has called for a “thorough and objective investigation” of the crash.