A Swiss research laboratory has found the radioactive substance Polonium-210 on the belongings of the late Palestinian President, Yasir Arafat.

According to Al-Jazeera, traces of the substance were found on a urine stain on his underpants, as well as on his toothbrush, raising questions about whether he was poisoned.

The former leader's wife Suha Arafat has now called for his body to be exhumed for tests, believing the traces suggest that Arafat ingested the toxic isotope.

This request has been agreed by the Palestinian Authority and Arafat's successor, Mahmoud Abbas, said they are prepared for a post-mortem nearly eight years after the former PLO leader's death in a military hospital outside Paris.

The exhumation is likely to re-ignite speculation that Mossad was behind Arafat's unexplained death, a theory held by many Palestinians.

Israel has always strongly denied involvement in Arafat's death.

Francois Bochud, head of the Institute of Radiation Physics in Lausanne, said: "We have an unexplained level of polonium, so this clearly goes toward the hypothesis of a poisoning, but our results are clearly not a proof of any poisoning."