Since Arafat's death, Palestinian society has long given currency to the rumour that he was murdered, with Israel the party most often blamed.
But there has never been any proof.
Arafat died in France on November 11, 2004 at the age of 75 after falling sick a month earlier, but doctors were unable to specify the cause of death and no post-mortem was carried out at the time.
In November 2012, his remains were exhumed and samples taken, partly to investigate whether he had been
poisoned with polonium
-- a suspicion that grew after the assassination in that manner of Russian ex-spy and Kremlin critic Alexander Litvinenko in London in 2006.
Speaking to reporters in Lausanne on Thursday, the Swiss team said the test results neither confirmed nor denied that polonium was the actual source of his death, although they provided "moderate" backing for the idea he was poisoned by the rare and highly radioactive element.
'France knows the truth'
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.
Bochud's lab measured levels of polonium up to 20 times higher than it is used to detecting.
Palestinian justice minister Ali Mhanna at Friday's news conference urged France to send findings from its investigation.
"We've so far received no response from the French side. We've sent a letter to the French demanding they accelerate the sending of results, and we're still waiting," said Mhanna.
"From the beginning the French have told us they can't send the results until there's Franco-Palestinian judicial cooperation," the minister added.
Read:Arafat's mysterious death becomes a whodunit
Tirawi declared that "France knows the whole truth and details of the martyrdom of Yasser Arafat".
Some 60 samples were taken from Arafat's remains in November 2012 and divided between Swiss and Russian investigators and a French team carrying out a probe at his widow's request.
So far, there has been no word on the French or the Russian test results.