A forensic study has concluded former Palestinian President Yasser Arafat may have been poisoned to death. Samples taken from Arafat’s body show he had 18 times the normal level of the radioactive material polonium. The team of Swiss scientists who examined Arafat’s remains says their findings “moderately support” poisoning as the cause of death. On Tuesday, Arafat’s widow called for an investigation at Arafat’s Ramallah headquarters, where he fell ill one month before dying in 2004. Speaking to Al Jazeera, forensic scientist David Barclay said he believes Arafat was poisoned.

David Barclay: “If I was a judge and jury, this is absolutely stone cold certain. This is beyond any doubt, in my opinion, that it was polonium that caused the death of Yasser Arafat.”

According to Barclay, the polonium found in Arafat’s body must have come from a nuclear reactor. Israel has denied responsibility for Arafat’s death. Other experts have questioned the poisoning theory, saying Arafat showed symptoms inconsistent with radioactive exposure.