Palestinian officials say Israel is the "only suspect" in the death of leader Yasser Arafat following a Swiss report that said his remains contained high levels of radioactive polonium.
The head of a Palestinian committee set up to investigate Arafat's 2004 death called it an "assassination".
He said investigations would continue "to confirm all the details and all elements of the case".
Israel has repeatedly denied any involvement in Arafat's death.
Arafat's widow, Suha, has said she believes the latest report proves he was assassinated. However, she said her late husband had many enemies around the world and she could not directly accuse anyone.
The Palestinian leader died in a military hospital in Paris in 2004 after suddenly being taken ill at his presidential compound in the West Bank city of Ramallah.
"We say that Israel is the prime and only suspect in the case of Yasser Arafat's assassination, and we will continue to carry out a thorough investigation to find out and confirm all the details and all elements of the case," Palestinian committee head Tawfik Terawi told a news conference in Ramallah.
It is not clear how the Palestinian investigators believe the poison was administered to Arafat, who was surrounded by guards and a close circle of aides at his compound.
The BBC's Yolande Knell, who was at Friday's hearing, said that in response to that question, the head of the committee said there had been a lot of interviews and he had "security information" but could not make details public at the moment.
A report by Swiss scientists said Arafat's remains contained "unexpectedly high" amounts of polonium-210. However, they could not confirm it had caused his death.
His remains were exhumed last year following tests on his belongings that suggested he could have been poisoned.
About 60 samples were divided between Swiss and Russian investigators and a French team carrying out an investigation at his widow's request.
France began a murder inquiry in August 2012 after the preliminary findings of polonium by the Swiss scientists, who have been working with an al-Jazeera documentary crew.
One Russian official said last month that no traces of polonium had been found.
Our correspondent says some Palestinian officials have already called for a new international inquiry into Arafat's death.
Scientists from the Vaudois University Hospital Centre (CHUV) in Lausanne, Switzerland, had carried out a detailed examination of Arafat's medical records, samples from his remains and items he had taken into the hospital in Paris.
The biological materials included pieces of Mr Arafat's bones and soil samples from around his corpse.
Prof Francois Bochud told a news conference on Thursday that the high level of polonium detected "by definition... indicates third party involvement... Our results offer moderate backing for the theory of poisoning".
But he added: "Was polonium the cause of the death for certain? The answer is no, we cannot show categorically that hypothesis that the poisoning caused was this or that."
The scientists said they had been unable to reach a more definitive conclusion because of the time passed since Arafat's death, the limited samples available and the confused "chain of custody" of some of the specimens.
Polonium-210 is a highly radioactive substance. It is found naturally in low doses in food and in the body, but can be fatal if ingested in high doses.
Arafat led the Palestine Liberation Organisation for 35 years and became the first president of the Palestinian Authority in 1996.
His official medical records say he died from a stroke resulting from a blood disorder.
Suha Arafat said she had no doubt her late husband had been assassinated but refused to point the finger at Israel.
"I can't accuse anybody. Everybody wants to accuse Israel - I can't accuse - I can't jump into conclusion," she told the BBC.
"Now the case is in the French jurisdiction, I wanted to document this crime - this crime I want it documented for history, actually."