If the world is looking for evidence, it is not hard to find. The poison that poured from the skies over several suburbs of Damascus on Wednesday may have killed hundreds, but it has left twitching, fainting, confused but compelling survivors.
"I was asleep," a 13-year-old boy called Abdullah told the Daily Telegraph yesterday. "Then my breath seized up. I tried the stairs but I couldn't find the steps: I had lost control of my body."
His father and brother are dead, he said, but his mother is still alive.
Mohammed Ibrahim, 24, described how he heard the explosion. "I ran outside to help," he said. "I saw women and children lying in the streets dying or collapsed or already dead, even babies.
"I became contaminated myself and fainted, and I don't remember anything after that. I just woke up two hours ago. But I have lost my cousins, a lot of my family, neighbours."
A team of United Nations weapons inspectors was yesterday closeted in a Damascus hotel just 20 minutes' drive from where Abdullah lay, recovering from whatever it was that apparently poisoned hundreds of men, women and children in the east of the city on Wednesday.
The usual diplomatic arguments broke out from New York to Moscow about whether they could make that short journey to determine who was responsible for the attack. But as the surviving residents emerged from unconsciousness, they gave their testimonies anyway.
Another even younger child, a boy who did not give his name, said he was given a mask as the attack broke out. It may have done some good as he survived with his sister, alone of their family.
"I put the mask on my mouth," he said. "My father was holding someone up but then he fell down himself. I said to him, 'What's wrong with you?' I picked up a pail of water and shoved my nose into it. I threw water over my family. I threw water over my younger sister and I put her into the ambulance.
"I stayed there running around, calling for help. My uncle came, and then he fainted too. I went outside calling for the ambulance again but nobody heard me. I went back inside, and there were my family again, all of them. I threw water on them but this time nobody woke up."
The team of United Nations weapons inspectors that landed in Syria on Sunday, with the regime's agreement, to investigate three other attacks, remained in their Damascus hotel yesterday.
The locations in the suburbs of East Ghouta and Zamalka where at least 10 missiles, apparently loaded with chemicals, landed on Wednesday night (NZT) are just 20 minutes' drive east. However, the inspectors only have permission to travel to the places already agreed after months of tortuous negotiations.
Last night, UN Secretary-General Ban Ki Moon demanded the Syrian Government allow inspectors to investigate "without delay". His spokesman said he was "deeply troubled", and was sending the UN head of disarmament, Angela Kane, to the capital. France suggested "force" should be used if the regime was found to be responsible for the attacks, while Britain said no option had been ruled out that might save civilian lives.
Barack Obama has ordered his intelligence agencies to establish urgently whether poison gas attacks was to blame as he weighs the United States response.
Russia, however, said the hundreds of deaths might be a "provocation" by the rebels timed to coincide with the inspectors' arrival.
Yet witnesses spoke of seeing the missiles - some caught on camera - coming from central Damascus. Weaponising chemicals on this scale, experts said, required a level of sophistication beyond that of the rebel forces.
The Syrian Army, on the other hand, is known to have the largest arsenal of such weapons in the Middle East and is trained in their use
What poison was used is unclear. One middle-aged man said the gas was yellowish and had an unpleasant smell, something confirmed by a number of the children. Sarin, the gas most commonly cited for its effect of constricting pupils, as seen in some of these cases, is odourless, while mustard gas, another part of the arsenal, causes blisters that the victims do not show. However, it is possible some combination was used.
The Syrian National Coalition gave a figure of more than 1300 dead with more bodies being found. The figures are hard to verify, but the bodies shown in videos online amount to the hundreds.
Ban had heard no response last night to his request to the Syrian authorities to allow the inspectors access.
The only comment from Damascus itself was that the allegations against the regime were "absolutely baseless".