Dramatic video recorded in the Syrian capital Damascus claimed to show regime forces using chemical weapons against rebel fighters, who survived with the help of gas masks.

On Monday, France’s foreign minister also said more signs had emerged of chemical weapons being used in Syria.

Laurent Fabius said outside a meeting of European Union foreign ministers in Brussels that there “are stronger and better substantiated indications of the local use of chemical arms. We have to check this and (we) are doing this with our partners.”

On Sunday, French paper Le Monde released a video by a reporter who was given access to Free Syrian Army fighters in the Ghuta neighborhood.

The cameraman followed the fighters as they scrambled through bombed buildings, following a route through rubble where walls were breached to provide access from one apartment to the next.

As shots rang out, the fighters could be seen quickly donning gas masks as a precaution against a chemical attack.

The rebels reported that the Syrian Army has used chemical weapons several times in previous months, with doctors confirming that victims showed symptoms of neurotoxins.

Syria is known to possess one of the world’s largest chemical weapons stockpiles, though Damascus has denied claims that it has used them against its own people.

France had been looking into reports of chemical weapon use since early this month, when the ministry said there were accounts and indicators on the use of chemical weapons in Syria’s civil war that needed to be verified.

In April, top officials from Israel, the US and other Western countries said they believed chemical weapons had been used in Syria

The US government has intimated in the past that the use of chemical weapons by the Syrian regime against its own people would potentially constitute the crossing of a “red line” for possible military intervention. Still, US President Barack Obama claimed a month ago that the intelligence about the use of chemical weapons in Syria was not yet sufficient.

Israel kicked off a drill on Monday to prepare the country in case of chemical attack, though officials say there is a low possibility of that occurring.

In the last two weeks, requests for gas masks have increased by 30 percent, a Home Front Defense source said Monday.