It looks like Arafat was murdered by the Israelis after all. No surprise there.

The Palestinian Authority has said it will exhume the remains of its late leader, Yasser Arafat, to investigate new claims that he was murdered with the radioactive isotope polonium-210, the same substance used to assassinate the Russian dissident Alexander Litvinenko.

The claim that Arafat – who died in Paris in 2004 – may have been poisoned first emerged in the immediate aftermath of his death and was revived earlier this week after a nine-month investigation by al-Jazeera, which was given access to Arafat's personal effects by his widow Suha.

"The Authority, as it always has been, is ready to completely co-operate with and clear the way for an investigation into the true causes leading to the martyrdom of the late president," said Nabil Abu Rudeineh, a spokesman for the Palestinian president, Mahmoud Abbas. He did not give a date for when this might occur.

Many Palestinians have long suspected that Arafat was murdered by Israeli agents.

Arafat's body is buried in a mausoleum at his compound where he was besieged and in effect confined by Israeli forces before his death.

The alleged detection of polonium on his toothbrush and on his clothes after an examination by the Institut de Radiophysique in Lausanne, Switzerland, has deepened the mystery over the cause of Arafat's death, but appears to contradict the restricted medical report produced by French doctors after Arafat died at Percy hospital in Paris.

That report, leaked to the New York Times in 2005, concluded that Arafat had died after a stroke after suffering from the blood disorder disseminated intravascular coagulation or DIC.

That in turned appeared to have been caused by a mystery infection the cause of which the French doctors were unable to diagnose at the time.

The French report was originally kept secret by doctors citing concern for Arafat's privacy.

However, no trace of metals or drugs was found by blood toxicology tests performed at three different laboratories: the criminal division of physics and chemistry at the Institute of Criminal Research of the National Gendarmerie; the department of clinical biochemistry, toxicology and pharmacology at Percy; and the French army's radiotoxicology control laboratory.

While it is known that Israeli officials – including the former Israeli president Ariel Sharon's then deputy Ehud Olmert – had discussed "eliminating" Arafat "as a terror head", the emergence of Arafat's effects after so long is unlikely to prove how he died, something only an autopsy is likely to reveal.

"I can confirm to you that we measured an unexplained, elevated amount of unsupported polonium-210 in the belongings of Mr Arafat that contained stains of biological fluids," François Bochud, director of the Lausanne institute, said in the documentary.

Bochud said the only way to confirm the findings would be to exhume Arafat's body to test it for polonium-210.

"But we have to do it quite fast because polonium is decaying, so if we wait too long, for sure, any possible proof will disappear," he added.

Polonium has a short half life – 138 days. Although it exists as a trace element, the levels found on Arafat's clothes, including on a urine stain, were almost nine times that found by the laboratory on a control sample.

Although Arafat is often described as having died after a sudden illness, his health had been declining. Those who encountered him in the months before his death noted a tremor in the Palestinian leader's hands.

Equally puzzling is the change in attitude of Arafat's widow, Suha, who was engaged in a battle with other members of his medical team over Arafat's care in his last days.

It was reported that there was no full autopsy after Arafat's death because Suha had refused permission.

Now, however, al-Jazeera quotes her as saying that she did want further blood tests from the Percy hospital but when she requested access, the hospital told her the samples had been destroyed.

"I was not satisfied with that answer," she told the television station. "Usually a very important person, like Yasser, they would keep traces – maybe they don't want to be involved in it?"

She told al-Jazeera: "At least I've done something to explain to the Palestinian people, to the Arab and Muslim generation all over the world, that it was not a natural death, it was a crime."

Dr Hanan Ashrawi, a senior figure in the Palestinian Liberation Organisation, said on Wednesday: "We believed all along Yasser Arafat was assassinated and now we have evidence that polonium was used and we are willing to co-operate in any way necessary with investigations to get to the truth.

"We suspect the people who repeatedly called for his death, including Ariel Sharon and others in Israel. We suspect those people in the region with access to polonium and we suspect the people who attempted to blow up his headquarters. We have circumstantial evidence indicating Israel – now we need concrete criminal evidence."

A senior Israeli official, speaking on condition of anonymity, dismissed the Palestinian accusations as "baseless", adding: "It was the Palestinians who made the conscious decision, for whatever reason, to keep Arafat's medical records closed to the public. Until those records are laid open, this is all pure conspiracy."

Polonium is a very rare natural element, which although it has been found in tobacco smoke produced in plants grown with phosphate fertilisers is extremely difficult to produce in significant quantities. Due to the sophisticated nature of the production process, it is made almost exclusively by national governments.

It does not emit gamma radiation, instead emitting alpha particles incapable of penetrating the human skin, so if Arafat was poisoned he would have had to ingest it.

There is very little scientific consensus about its effect on the human body. Clayton Swisher, the al-Jazeera reporter behind the investigation, points out that three of the six known deaths due to polonium exposure occurred in Israel in the 1960s.

"While I am not accusing them, Israel does possess polonium and has seen first-hand its effects," he said.

Swisher, who describes Arafat's death as a "great injustice", suggests his report may have produced the first tangible evidence that it was the result of "foul play".