Palestinian leader Yasser Arafat's remains showed test results consistent with polonium poisoning, but are not proof that he died that way, two experts have said.
The two Swiss forensic experts were part of an international team that opened Arafat's grave in the West Bank city of Ramallah last November.
They took samples from his body to see if there was evidence he was poisoned with the radioactive element.
Their report was released yesterday.
Patrice Mangin, director of Lausanne University Hospital's centre of legal medicine, said: "Our observations are coherent with a hypothesis of poisoning, in any case more consistent than with the opposite hypothesis (of no poisoning)."
Francois Bochud, director of the university's Institute of Radiation Physics, said the evidence was not conclusive.
He said: "Can we say with certitude that polonium was the cause of death of President Arafat?
"Unfortunately for those of you who want a clearly-defined answer, the answer is no.
"That is to say, our study did not permit us to demonstrate categorically the hypothesis of poisoning by polonium."
Their technical report of 108 pages was handed over on Tuesday at a secret meeting in a Geneva hotel to his wife Suha and the Palestinian Authority, the two parties who commissioned the investigation.
Report opens 'gates of hell'
The report opened "the gates of hell", one insider told Reuters.
There are few known cases of polonium poisoning, the most famous recent example being that of defecting Russian spy Alexander Litvinenko, who drank a poisoned cup of tea in a London hotel in 2006.
From his deathbed, Litvinenko accused Russian President Vladimir Putin of ordering his murder.
Mr Bochud said a few micrograms of polonium would be enough to kill somebody.
"For example, it could be put in a drink, or food would be a possibility, five micrograms is almost nothing at all," he said.
"What we know about the time lag between ingestion of radioactive poisoning and death is that usually it lasts around one month.
"This is commonly observed in radiation poisoning and this is actually also the case that we observed with Mr Arafat."
Arafat's widow Suha yesterday said they were revealing a real crime and "a political assassination".
She said: "It is scientifically proved that he didn't die a natural death and we have scientific proof that this man was killed."
She told Reuters the polonium must have been administered by someone "in his close circle" because experts had told her the poison would have been put in his coffee, tea or water.
She did not accuse any country or person, and acknowledged that the historic leader of the Palestine Liberation Organisation had many enemies, although she noted that Israel had branded him an obstacle to peace.
Israel denied any involvement in his death.
No autopsy was carried out on Arafat, whose official cause of death was a stroke.
The Swiss report said that blood, urine, faecal and cerebrospinal samples taken during his hospitalisation in France were "subsequently destroyed".