According to a Guardian report, both the British and French governments claim to have found evidence for sarin in urine and blood samples smuggled out of Syria by French journalists. Fabius stated that the French government has provided its findings to a UN investigation into chemical weapon use in Syria. Though it is still unclear whether the Syrian government or rebels used Sarin gas first, Fabius stated that there is now some proof that it has been used by the Syrian government. He said that France would be talking with the U.S. and U.K. about possible reactions to the news.
Sarin is a nerve agent that has been classified as a weapon of mass destruction by the UN. As a chemical weapon, sarin can be inhaled and absorbed through the skin. Contact with the gas can cause loss of muscle control, including the muscles involved in breathing, leading to asphyxiation.
Syria has been embroiled in a civil war since 2011, when government forces began firing on "Arab Spring" protesters. The protesters soon organized into armed militias, and a sporadic war has continued to be waged across the country. The UN estimates that around 80,000 Syrians have died during the civil war.