Once the Russian, French and Swiss experts had taken samples from the remains, the tomb was re-closed with a modest military ceremony and fresh wreaths were laid outside the mausoleum.

“This was a painful day,” Dr. Abdullah Bashir, one of Mr. Arafat’s personal physicians, said at a news conference after the ceremony. “We have the right to ask questions. We will continue to seek the truth.”

Many Palestinians suspect that Mr. Arafat was poisoned by Israel – a charge that Israeli officials have strenuously denied.

The exhumation took place eight years after Mr. Arafat’s death in a Paris hospital in 2004 at age of 75. It was the result of a television investigation into the cause of his death, which has long remained shrouded in contention and mystery.

Mr. Arafat became ill in October 2004 after being confined under an Israeli Army siege and virtual house arrest for more than two years in the compound where he is buried. At the time, the area was seething with the violence of the second Palestinian intifada, or uprising, and the Israeli clampdown.

He was flown by helicopter out of his headquarters and transferred to a French military hospital, where he died about two weeks later of unannounced causes.

The records showed that he had died of a stroke that resulted from a bleeding disorder caused by an underlying infection. The infection was never identified. The hospital found no traces of poisons it had tested for.

But in July, Mr. Arafat’s widow, Suha, called for an exhumation in an interview with Al Jazeera, the Arabic television channel based in Qatar, after it reported that Mr. Arafat might have been poisoned with polonium, a radioactive element associated with K.G.B.-style assassination intrigue.

With Mrs. Arafat’s help, the news channel carried out what it called an in-depth investigation into the circumstances surrounding Mr. Arafat’s death.

Mrs. Arafat gave the broadcaster a copy of Mr. Arafat’s medical records as well as personal effects, including clothing he had worn during the period just before he fell ill, his toothbrush and his trademark black-and-white checkered headdress. Al Jazeera said it took the items to the best laboratories in Europe for forensic testing.

At the University of Lausanne’s Institute of Radiation Physics in Switzerland, doctors found what they said were unusually high levels of a highly toxic radioactive isotope, polonium 210, in certain items but added that further testing of Mr. Arafat’s remains would be necessary before determining whether he had been poisoned.

Mrs. Arafat requested that the French authorities open a murder inquiry. Mahmoud Abbas, the Palestinian Authority president and Mr. Arafat’s successor, then said that Russian experts would help with the investigation.