Palestinian officials have begun preparing the gravesite of Yasser Arafat for the planned exhumation of his remains, expected later this month.
Officials erected a blue tarp meant to prevent onlookers from seeing activities inside the grave, located near government headquarters in Ramallah.
The street leading to the grave has also been closed.
Officials could be seen inside the mausoleum but it was not clear if they were local or foreign.
Russian, French and Swiss investigators are set to exhume the remains.
Some of the teams have already visited the grave to determine how best to dig up the remains.
Arafat's death in a French hospital in November 2004 has remained a mystery for many.
While the immediate cause was a stroke, the underlying source of an illness he suffered in his final weeks has never been clear.
That led to conspiracy theories that he had cancer, AIDS or was poisoned. Many in the Arab world have blamed Israel, which vehemently denies the charge.
The new probe comes after a Swiss lab discovered traces of a deadly radioactive isotope on clothes said to be Arafat's, sparking new accusations he was poisoned.