Inspectors from the Organisation for the Prohibition of Chemical Weapons (OPCW) are attempting to access the previously rebel-held town of Douma, where medical organisations and rescue workers say President Bashar al-Assad's forces dropped bombs filled with toxic chemicals in an attack on 7 April, killing more than 40 people.
The Syrian government and its key ally, Russia, say the incident was staged. But the US, UK and France – who support the opposition to Mr Assad – say they are confident that chlorine and possibly a nerve agent were used.
Despite the uncertainty about what happened in Douma, a cluster of influential social media activists is certain that it knows what occurred on 7 April.
