The OPCW has said its data provided "reasonable grounds" an attack took place, but assigned no blame.Read more
Suspected Syria chemical attack
Abdul Hamid Youssef describes how he lost his wife, his twins and other family members in a chemical attack.
After seven years of civil war in Syria, President Bashar al-Assad appears close to victory against the forces trying to overthrow him.
A BBC investigation shows the extent to which chemical weapons have been crucial to his war-winning strategy.