WASHINGTON, United States (AFP) — The United States believes the nerve agent sarin was used in addition to chlorine in an alleged Syrian atrocity that provoked Western military strikes, a senior official said Saturday.

The senior US official, speaking on condition of anonymity, said analysis of images and witness accounts from the scene of last week’s attack in Douma pointed to the use of the banned agent.

“And while the available information is much better on chlorine use, we do have significant information that also points to sarin use,” the official said.

“We’ve got symptoms described in reports of media and NGOs and other sources. They do point to miosis or constricted pupils, convulsions and disruptions to the central nervous system,” she said.

“Those symptoms don’t come from chlorine. They come from nerve agents. These symptoms — in addition to the dozens of deaths and hundreds of injuries reported — also suggest sarin.”

International experts from the Organisation for the Prohibition of Chemical Weapons have not yet been able to study the aftermath of the attack, a former rebel bastion in the Damascus suburbs.

But Syrian President Bashar al-Assad’s regime has been accused in the past of using sarin, sometimes mixed with chlorine, in attacks which has left scores dead, including women and children. US, French and British officials cited the Douma attack in justification for their overnight air and cruise missile strikes on alleged regime chemical weapons sites.

They also allege that Assad’s forces have repeatedly deployed chemical weapons in attacks over the previous year, but the use of sarin is seen as an escalation.

“It’s a much more efficient weapon, unfortunately, the way the regime has been using it, and it results in higher deaths and the deaths, according to the photos of multiple children and women,” the official said.