French President Emmanuel Macron has threatened to “strike” Syria if proof emerges that its government is using chemical weapons against civilians.
“We will strike the place where these launches are made or where they are organised,” he told reporters.
But Mr Macron said French intelligence had so far found no evidence that banned chemical weapons had been used.
Nine people were treated for breathing difficulties after a bomb believed to be filled with the chemical was dropped on a rebel-held town earlier this month.
The Syrian opposition said a government helicopter dropped the bomb on Saraqeb, in the north-western province of Idlib.
The Syrian government strongly denies using chemical weapons and says it does not target civilians.