Their investigation was one of three carried out on his remains in 2012. Arafat died in Paris in 2004, aged 75.
Last month, Swiss scientists said they had detected high levels of radioactive polonium but could not say if it had caused his death.
A French inquiry is also said to have found he was not a victim of poisoning.
Comment: From this article, here were the:
Three parallel inquiries
Swiss report - 8 Nov 2013: High levels of polonium; moderate backing for poisoning theory
French report - 3 Dec 2013: Source says poisoning theory rejected in favour of death by natural causes
Russian report - 26 Dec 2013: Death by natural causes not from radiation exposure