PARIS — France said Tuesday it has confirmed that the nerve gas sarin was used “multiple times and in a localized way” in Syria, including at least once by the regime. It was the most specific claim by any Western power about chemical-weapons attacks in the 27-month-old conflict.
Britain later said that tests it conducted on samples taken from Syria also were positive for sarin.
The back-to-back announcements left many questions unanswered, highlighting the difficulties of confirming from a distance whether combatants in Syria have crossed the “red line” set by President Barack Obama. The regime of Syrian President Bashar Assad has refused to allow U.N. investigators into the country.
The French and British findings, based on samples taken from Syria, came hours after a U.N. team said it had “reasonable grounds” to suspect small-scale use of toxic chemicals in at least four attacks in March and April.
The U.N. probe was conducted from outside Syria’s borders, based on interviews with doctors and witnesses of purported attacks and a review of amateur videos from Syria. The team said solid evidence will remain elusive until inspectors can collect samples from victims directly or from the sites of alleged attacks.
Some experts cautioned that the type of evidence currently available to investigators — videos, witness reports and physiological samples of uncertain origin — leaves wide doubts.
At the same time, forensic evidence of alleged chemical weapons use is fading away with time, and the longer U.N. inspectors are kept out of Syria, the harder it will be to collect conclusive proof, they said.
Syria is suspected of having one of the world’s largest chemical weapons arsenals, including mustard and nerve gas, such as sarin.