Experts from the Organisation for the Prohibition of Chemical Weapons (OPCW) arrived in Damascus last weekend to examine the site of the suspected attack in nearby Douma, which killed dozens of people and led to US-led missile strikes.
"At this time, inspectors from the OPCW still don't have access to the site of the gas attack in Douma," Le Drian said in a written statement.
The obstruction is likely aimed at ensuring that proof of the attack disappears, he said, adding that the OPCW must have full, immediate and unimpeded access to the site.