New radiation tests on the clothes and belongings of Palestinian leader Yasser Arafat have led to speculation he died from poisoning by polonium.

Researchers at the Institute of Radiation Physics at Lausanne in Switzerland conducted tests on the clothing Mr Arafat was wearing when he died in 2004, as well as personal belongings, including a toothbrush.

Francois Bochud, the head of the Swiss institute, said the belongings were given to Mr Arafat's widow Suha by the military hospital in Paris where he died. All had been stained by his sweat, saliva, urine or blood.

Dr Bochud says the team measured an unexplained, elevated level of unsupported polonium-210.

"The conclusion was that we did find some significant polonium that was present in these samples," he told Al Jazeera.

Dr Bochud says to confirm that polonium was indeed what killed Mr Arafat, Suha would have to agree to his body or some of his remains being exhumed for analysis.

Mr Arafat's death at the age of 75 in a French hospital was surrounded by mystery and allegations he had been poisoned.

He had reportedly been in good health until shortly before he fell ill.

French authorities refused to reveal the precise illness or cause of death, which only fuelled the rumours.

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At the time Palestinian officials said the leader's French doctors had performed toxicological tests and found "no known poison".

Scientists at the institute in Switzerland say they did more sophisticated testing for less conventional toxins including radioactive elements.

Another spokesman for the institute, Darcy Christen, told Reuters that clinical symptoms described in Mr Arafat's medical reports were not consistent with polonium-210.

He stressed that conclusions could not be drawn as to whether the Palestinian leader was poisoned or not.

Polonium was used to kill Russian former spy turned Kremlin critic Alexander Litvinenko, who died in 2006 after drinking tea laced with the radioactive substance at a London hotel.

"If we take the scenario of Mr Litvinenko, one gigabecquerel at the beginning would come to about 10 millibecquerel," Dr Bochud told Al Jazeera.

"What was astonishing in our case was that we found values in the samples of Mr Arafat that were in the same order of magnitude."

Al Jazeera's documentary claims unsupported polonium is the kind made in a nuclear reactor and even the tiniest amount, not even visible to the naked eye, is enough to kill.

Even if Mr Arafat's body was to be exhumed, it is unlikely any further tests would prove any individual or state was behind his death.

ABC/wires