Forensic tests on the exhumed remains of former Palestinian leader Yasser Arafat, who died in November 2004, have shown unexpectedly high levels of radioactive substance polonium-210, which may support theories that he was poisoned. (Chris Hondros/Getty Images)

On the evening of Oct. 12, 2004, Yasser Arafat, the flamboyant, autocratic and inscrutable chairman of the Palestine Liberation Organization, sat down for dinner at his besieged compound in Ramallah in the West Bank. And so began one of the great medical mysteries in the modern Middle East.

A month later, Arafat was dead in a French hospital.

By natural causes? Or was it a murder most foul? Theories have swirled in the past nine years that Arafat was assassinated, perhaps poisoned — by rivals, by his inner circle, by Israeli agents.

On Wednesday, a final 108-page report by a team of Swiss experts revealed that tests on Arafat’s exhumed remains and possessions — a shaft of his hair, a urine stain on his underwear, a woolen cap — “moderately support the proposition that the death was the consequence of poisoning with polonium-­210,” a highly radioactive substance 250,000 times as toxic as cyanide.

“This has confirmed all our doubts,” Arafat’s widow, Suha, told the Reuters news agency. “It is scientifically proved that he didn’t die a natural death, and we have scientific proof that this man was killed.”

Suha Arafat, speaking in Paris, called her husband’s death “a real crime, a political assassination.”

She did not name any suspects, but if her husband truly was killed, there would be many. He had myriad enemies — not least the Israeli government.

Arafat spent his life battling the Israelis, first as a guerilla fighter and later as a statesman. For decades, he served as leader of the Fatah movement and the face of the PLO, always in his olive green uniform, patchy grey beard and checkered scarf.

His critics called him a terrorist and a crook, and they accused him of amassing a personal fortune and ultimately failing the Palestinian cause. His supporters revere him as a kind of founding father, and his portrait hangs on the wall of every Palestinian Authority functionary in the West Bank.

Before his death in 2004 — more than a decade after he signed the Oslo Accords, which offered a still-unfulfilled promise of peace — Arafat was confined to his Ramallah compound by the Israeli military. The second intifada, or uprising, was raging in Israel and the occupied territories as a wave of Palestinian suicide bombers was met with a fierce Israeli crackdown.

Israeli officials have repeatedly denied that their government had anything to do with Arafat’s death.

Israeli Foreign Ministry spokesman Yigal Palmor told the Jerusalem Post on Wednesday that the Swiss findings were “more soap opera than science,” calling them part of the ongoing battle between Arafat’s widow and the Palestinian Authority.

Suha Arafat, a secretary and interpreter who in 1990 married the longtime bachelor who was more than twice her age, has had a strained relationship with the Palestinian leadership. She has been accused of living in luxury, siphoning off Arafat’s millions. She resides in Paris, not in the Palestinian territories, and has been quoted as saying that she tried to divorce Arafat “a hundred times.”

In addition to the Israelis, suspects in Arafat’s killing — if that is, in fact, what it was — have included Palestinian rivals.

Palmor brushed off the idea that Arafat died of anything other than natural causes.

“It is all very, very confused and unclear,” he said. “What is clear is that there are huge holes in the theory, more holes than in Swiss cheese.”

The formal investigation into Arafat’s death began last year when a French magistrate opened a homicide inquiry. The decision came after Swiss scientists, working with the Al Jazeera news network, issued their initial reports that traces of polonium-210 were found on Arafat’s effects.

At the urging of Arafat’s widow, and supported by an Al Jazeera documentary crew, the Palestinian Authority permitted the exhumation of his body — along with soil and his shroud — from his tomb in Ramallah last November.

The final Swiss report, made public by Al Jazeera on Wednesday, offered evidence to support the theory that Arafat was poisoned. But it was also cautiously worded.

The Swiss scientists noted that polonium-210 decays rapidly; that Arafat’s remains were collected eight years after his death; that no autopsy was performed at the time of his death; and that polonium poisoning usually is accompanied by hair loss and immune suppression, which apparently was not the case with Arafat.

Yet the scientists also found that some of the 38 samples they examined showed “unexpectedly high” levels of polonium in radio-toxicological studies.

Shortly after finishing his meal that night in October 2004, the Swiss team said, the 75-year-old Arafat, who was considered to be in good general health for a man his age, showed immediate signs of distress: extreme nausea, vomiting, abdominal pain and diarrhea.

His condition deteriorated. Seventeen days later, the Israelis allowed Arafat to travel to the Percy Military Hospital in France, where he died Nov. 11, 2004.

His French doctors concluded that the cause of death was disseminated intravascular coagulation — essentially, blood clots throughout the body.

No autopsy was performed.

Palmor, the Israeli spokesman, suggested that if radioactive traces of polonium were found, they could have come from Arafat’s offices or residence.

Arafat’s remains have been examined by two additional forensic teams, but the results have not been made public.

The head of the Russian Federal Medico-Biological Agency, Vladimir Uiba, whose team conducted tests, was quoted by the Interfax news agency last month as saying that the PLO leader “could not have been poisoned by polonium.”

“The Russian experts who conducted the investigation did not find traces of this substance,” according to the Interfax report.

Later, the Russian institute denied the report. “We have not publicized any official results of our forensic review,” a spokesman told the Agence France-Presse news agency.

A French team is also investigating the remains.

Ibrahim Khraishi, the Palestinian Authority’s representative at the United Nations’ office in Geneva, told the Palestinian news agency Ma’an that Palestinian officials have established an ad-hoc committee to review the reports and will announce results soon.