TOTAL 16 ALLEGATIONS

Rebels have seized all kinds of weapons from military depots across Syria, according to the United Nations. Western powers say the rebels do not have access to chemical arms.

UN Secretary-General Ban Ki-moon established the Sellstrom investigation after the Syrian government wrote to Ban accusing the rebels of carrying out the chemical weapons attack in Khan al-Assal.

Sellstrom delivered the final report to Ban on Thursday. Ban will brief the UN General Assembly on the report on Friday and the UN Security Council on Monday.

"The use of chemical weapons is a grave violation of international law and an affront to our shared humanity," Ban said. "We need to remain vigilant to ensure that these awful weapons are eliminated, not only in Syria, but everywhere."

The United Nations has now received 16 reports of possible chemical weapons use in Syria, mainly from the Syrian government, Britain, France and the United States. The experts looked closely at seven of those cases.

The UN experts were from the Organization for the Prohibition of Chemical Weapons and the World Health Organization.

France, Britain and the United States said the technical details of Sellstrom's initial September report on the August 21 attack pointed to government culpability, while Syria and Russia blamed the rebels.

Syrian President Bashar al-Assad's government agreed to destroy its chemical weapons arsenal after the August 21 Ghouta attack, which had led to threats of U.S. air strikes. Syria also acceded to the Chemical Weapons Convention.

The UN Security Council adopted a resolution in September to enforce the deal, brokered by the United States and Russia, which requires Syria to account fully for its chemical weapons and for the arsenal to be removed and destroyed by mid-2014.

The Hague-based Organization for the Prohibition of Chemical Weapons has been charged with supervising the elimination of Syria's chemical arsenal.