Arafat, aged 75, died in Paris on November 11, 2004 after falling sick a month earlier. Doctors were unable to specify the cause of death and no post-mortem was carried out.
Palestinian society has long given currency to the rumour that Arafat was murdered, with Israel the party most often blamed.
But there has never been any proof.
"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," said Tawfiq Tirawi, head of the Palestinian Authority's inquiry into the death.
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.
"The Palestinians should stop levelling all these groundless accusations at Israel without the slightest proof. Israel did not do it. Enough is enough."
In November 2012, Arafat's remains were exhumed and samples taken, partly to investigate whether he had been poisoned with polonium. That suspicion had grown after the assassination in that manner of Russian ex-spy and Kremlin critic Alexander Litvinenko in London in 2006.
Tirawi said Palestinian investigators had studied the findings of Swiss scientists released this week which "moderately" supported the notion of poisoning.
They said the quantity of the deadly substance found on his remains pointed to the involvement of a third party.
"We can't say that polonium was the source of his death...Nor can we rule it out," said Professor Francois Bochud of the Lausanne Institute of Applied Radiophysics.