1Tests on the remains of Palestinian leader Yasser Arafat have neither confirmed nor ruled out polonium as a cause of death, but indicate a third party was involved, Swiss experts said Thursday. "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, adding that the amount of polonium in Arafat's remains indicate third party involvement.