A Palestinian woman walks past a mural on the controversial Israeli barrier depicting the late Palestinian leader Yasser Arafat, at Qalandiya checkpoint near the West Bank city of Ramallah Nov 26, 2012. [Photo/Agencies]

RAMALLAH - Palestinian engineers have started working to exhume late leader Yasser Arafat's remains in the West Bank city of Ramallah at dawn Tuesday, sources said.

The sources added that the engineers started removing sand around the tomb. Four meters beneath it, a movable layer of cement is located. The sand was brought from Jerusalem when Arafat was buried here on April 11, 2004.

The remains will be dug up within one hour with senior Palestinian officials attending the process along with experts and investigators from Switzerland, France and Russia, the sources added.

Tight security measures were taken to ensure the secrecy of the process.

The investigation aims to find out if Arafat's death in a French hospital resulted from poisoning. The Palestinians suspect that Israel had poisoned Arafat when he was besieged in his Ramallah headquarters before falling ill.

Earlier this year, Swiss experts tested Arafat's personal belongings as part of a documentary aired by al-Jazeera, the Doha-based pan-Arab TV channel. The report cited the Institute of Radiation Physics as saying that traces of radioactive polonium-210 were found on Arafat's underwear and toothbrush.

Arafa's widow, Suha, filed a civil lawsuit at a French hospital asking for a murder investigation into her husband's death. The Palestinian leadership also decided to bring in the Russians for more credible inquiry.