Still, rebel leaders and opponents of the Assad regime insisted that it was newly guilty of war crimes.
“The chemical weapons massacre had more than 1,500 martyrs and 5,000 wounded, most of them women and children,” said Abu Mansour, an activist based in the area of Reef Damascus. He claimed that chemical munitions were dropped on the suburbs of Ein Tarma, Zamalka and Jobar.
Mohammed Salaah al Din, another activist from the area, said sarin gas shells began to hit the area shortly after 2 a.m. Wednesday. He claimed that some 1,650 people were dead, that 5,000 had been wounded and that physicians had confirmed the presence of the nerve gas.
Mutasem Billah, a rebel supporter from the outskirts of eastern Damascus, said by Skype that he’d seen a chemical weapons strike less than a half-hour later. He counted 29 rockets that he said were armed with chemical warheads.
“They were launched at five points in the eastern Ghouta, and the doctors told us that it was sarin gas,” he said. He estimated the dead at 1,160 and the wounded at closer to 7,000. “Most . . . are women and children.”
Their symptoms, he said, included vomiting, panic attacks and contracted pupils.
The activists who made the claims conceded that they hadn’t yet had time to smuggle blood and tissue samples out of Syria – they’ve done so before – to confirm the use of nerve gas.
That left experts with only inconclusive videos to analyze. One forensic expert questioned whether panicked victims assumed they’d been hit by nerve agents and then misused medicine.
“There seem to be increasing amounts of footage of very realistic-appearing injuries commensurate with a chemical attack, but (that is) still leaving lots of questions,” said Stephen Johnson, a visiting fellow at Cranfield University’s Forensics Institute in Great Britain. “It would appear that patients have been injured by what might be a rapid attempt to inject atropine,” a potentially poisonous compound that’s sometimes used as an antidote to sarin exposure.
Johnson noted that videos had moved to the Internet quickly early Wednesday. More typically, footage from the rebel side is posted gradually over the course of a day or longer. It can be difficult to access the Web in the area amid regular power outages and ongoing fighting.
Still, some of the symptoms are commensurate with exposure to nerve gas, “which might be sarin,” he said. “But you can’t tell that in a video.”
Thielmann, the arms control specialist, thought the White House was correct to be cautious before targeting Syria’s chemical weapons facilities.
“The knowledge is always imperfect, and we don’t always know where these things are,” he said. “In some ways, we are safest with the Syrian government maintaining control of these assets.”
The Syrian army is widely thought to have extensive Cold War-era stockpiles of chemical weapons. Whether the government’s military forces have used it, however, has been open to debate.
American and European officials have said that deploying chemical munitions would cross a “red line,” likely forcing them to intervene in the conflict with military might.
A revelation that some chemical weapons might have been used in previous attacks – apparently verified in blood and tissue samples that activists smuggled out of Syria – led Obama to announce his willingness to arm some rebel groups two months ago.