International investigators said Monday that the demolition of Syria's chemical weapons production units had begun.

"Destruction operations commenced in December," Organization for the Prohibition of Chemical Weapons (OPCW) spokesman Peter Sawczak told news agency AFP. The OPCW is overseeing the elimination of chemical stockpile in Syria.

The destruction program is a key part of the destruction of Syria's chemical weapons stockpile, ordered by the UN Security Council in September 2013. The production facilities to be demolished include 12 hangars and tunnels, which were supposed to have been eliminated last December, but work was stalled when the contractor pulled out.

The OPCW said in its latest report that the destruction of the 12 facilities was now expected to be completed by the end of June.

In August 2013, Syrian government rockets fired weapons containing the poisonous sarin gas outside Damascus, killing nearly 300 people and prompting the international community to pressure President Bashar al Assad into turning in his chemical weapons.

Following the incident, nearly 1,300 metric tons of chemical weapons were removed from Syria and most were destroyed aboard the US Navy ship Cape Ray.

The OPCW is also looking to allegations claiming the use of chlorine "for hostile purposes."

mg/bw (AFP, AP)