Western intelligence agencies are seeking biological samples from survivors of the chemical weapons attack in northern Syria to compare against specimens of sarin taken from the Syrian military’s stockpiles four years ago.

The testing will be used to established whether the nerve agent used in the attack – which the US, Britain and France say is very likely sarin – came from stores of the gas that Damascus was supposed to surrender in a UN-supervised process after more than 1,300 people were killed in an attack in August 2013. Intelligence officers are also seeking environmental samples from the town of Khan Sheikhun in Idlib province where, according to witnesses, a dawn airstrike on Tuesday released a noxious gas over the area, killing at least 70 people and wounding more than 100.(guardian)…[+]