Two cylinders seized by Syrian government troops in an area held by foreign-backed militant groups contained deadly sarin

Two cylinders seized by Syrian government troops in an area held by foreign-backed militant groups contained deadly sarin, U.N. Secretary-General Ban Ki-moon said in a letter to the U.N. Security Council published Monday.

Ban said that on June 14, the Organization for the Prohibition of Chemical Weapons United Nations Joint Mission overseeing the destruction of Syria’s chemical stockpile analyzed the contents of the cylinders.

“The Joint Mission confirmed that these (cylinders) contained sarin,” read Ban’s letter, adding that the containers were “reportedly seized by the armed forces of the Syrian Arab Republic in August 2013 in an area” under the control of militant groups.

OPCW chief Ahmet Uzumcu said in a report attached to Ban’s letter that the Syrian government told the organization “the items did not belong to it.”