Al Jazeera's Investigative Unit has obtained the 15-page conclusion of a study by Russian scientists into the death of Yasser Arafat.
While a Swiss report found significant levels of polonium in Arafat’s pelvis and ribs, the Russian investigation team says its results are inconclusive.
The conclusion ultimately treats the cause of death by high dosage of polonium penetration as "unsubstantiated".
The Russian exhumation team received 20 samples from Arafat’s body, as did the Swiss and French teams. But the scientists in Moscow appear to have only been given four samples to test, two from the skull bone and two from "extremity bones".
Dr. Francois Bochud, who led the Swiss investigation, told Al Jazeera's David Poort that the skull was an unlikely place to test for the radioactive substance.
"We thought that [the skull] would not be the best kind of bone sample to measure," he said. "It is not as vascularised as other bones and therefore not the bone that would collect the highest quantity of polonium."
Dave Barclay, a veteran forensic scientist and investigator, told Al Jazeera, "the choice of bone fragments that they've chosen to use is very odd and the levels they've got appear to be 10 or 20 times less than you'd expect just from anyone else in the world."
"I think the results are meaningless," he said.
'An inferior study'
The Russian exhumation report concludes that "only one of the four provided fragments", a piece of the skull bone, "was found to have radioactive background".
In addition to being given an incomplete selection of bone samples, the scientists appear to also have been restricted by the Russian Foreign Ministry in how to present the report.
"The laboratory personnel say they received clear instructions from the Foreign Ministry on how the final report should look like," the source who leaked the report told Al Jazeera.
"It seemed suspicious to them that they were being asked to fill out a specific table and answer specific questions from the Foreign Ministry. Namely, to conduct an inferior study."
The source added that, "Russia's goal was to fulfill the Palestinian Authority's request, not offend Israel by helping the PA, and not create a new hotbed in the Middle East".
"Therefore, the objective here was to make a conclusion without a conclusion," he said.
Israel suspect in assassination
Palestinian investigators have said they are confident that former leader Yasser Arafat died of poisoning, citing Swiss and Russian reports.
Speaking at a news conference in Ramallah on Friday, members of the Palestinian Investigatory Committee on Arafat's death accepted the Swiss findings.
"We say that Israel is the one and only suspect in the case of Yasser Arafat's assassination, and we will continue to carry out a thorough investigation to find out and confirm all the details and all elements of the case," Tawfiq Tirawi, head of the Palestinian Authority's inquiry into the death, said.
"This is the crime of the 21st century," Tirawi told a news conference in Ramallah.
"The fundamental (goal) is to find out who is behind the liquidation of Yasser Arafat."
Israel once again firmly denied killing Arafat.
"I will state this as simply and clearly as I can: Israel did not kill Arafat. Period. And that's all there is to it," foreign ministry spokesman Yigal Palmor told AFP news agency.
Arafat’s body was exhumed in November last year, eight years after he died in a French military hospital, after Al Jazeera worked with Swiss scientists and found high levels of polonium in Arafat’s blood and urine, which stained his clothes.
The Palestinian Authority welcomed the investigation and also called for an independent investigation by Russia.