Outside experts have also voiced skepticism, noting that video footage showed that medical personnel treating victims did not don protective garments or masks. If there had been an attack with sarin or VX gas, the deadliest agents in Syria’s extensive arsenal, most of the people present would have been fatally or seriously contaminated, said Jean Pascal Zanders, a chemical weapons expert for the European Union. “Fatalities happen literally within minutes or even seconds,” he said. “There’s nothing that suggests that these people were even remotely exposed to nerve agents.”
Difficulty gathering evidence
Tests of nuclear devices send plumes of radiation into the atmosphere that aircraft can detect and analyze. By contrast, chemical munitions such as sarin evaporate quickly, leaving few recoverable traces even within the immediate radius of an attack.
The United Nations plans to send a team into Syria to investigate the Aleppo strike and similar incidents. Secretary General Ban Ki-moon sent a letter to the Syrian government Friday requesting expanded access for U.N. investigators to all sites where chemical weapons are suspected of being used, even in small doses.
A European official said, “We need to know what the precise details were, who was affected and how.”
But U.S. officials said there is likely to be scant physical evidence by the time experts reach the village where last week’s attack occurred. As a result, experts must rely mainly on reports from witnesses and monitoring the symptoms of those who may have been exposed.
The CIA, the National Security Agency and other spy services have expanded their collection efforts against Syria over the past year. But U.S. officials said that the CIA has not established a presence in the country and that the scope of the conflict has precluded it from distributing sensors that could detect chemical attacks.
Asked whether such devices were being used, one senior U.S. official said, “I wish.”
Instead, U.S. spy agencies are relying on a combination of satellite imagery, intercepted communications between Syrian officials, and reports from allies, including France, seen as having deeper networks of sources inside the country.
Last year, images helped confirm suspicions that the Syrian military was moving some of its chemical munitions. Intercepts have also led some U.S. officials to conclude that Assad is prepared to use chemical weapons as his hold on the country deteriorates.
“It looks clear that Assad would have used them at least two or three times in the past, had the administration not warned them explicitly,” said a former U.S. official who participated in high-level discussions about Syria. “Most people think it is a matter of time before they actually do.”