Western intelligence agencies are seeking biological samples from survivors of the chemical weapons attack in northern Syria to compare against specimens of sarin taken from the Syrian military’s stockpiles four years ago.
The testing will be used to established whether the nerve agent used in the attack – which the US, Britain and France say is very likely sarin – came from stores of the gas that Damascus was supposed to surrender in a UN-supervised process after more than 1,300 people were killed in an attack in August 2013.
Intelligence officers are also seeking environmental samples from the town of Khan Sheikhun in Idlib province where, according to witnesses, a dawn airstrike on Tuesday released a noxious gas over the area, killing at least 70 people and wounding more than 100.
The samples are expected to behand delivered in some cases and also collected from hospitals inside Turkey, where several dozen seriously ill people are being treated by medics.
In a suspected nerve gas attack in eastern Hama last December, agencies were unable to retrieve samples from victims. Khan Sheikhun, however, is much closer to the Turkish border and survivors continued to be ferried to crossing points throughout Wednesday.
The World Health Organization said some patients were showing symptoms of exposure to a nerve agent, including life-threatening breathing difficulties. It said hospitals inside Syria were struggling to cope with gravely ill patients and confirmed that one hospital treating the victims had been hit by an airstrike on Tuesday.
Few hospitals in Idlib have the capacity to deal with the symptoms of chemical attacks after the repeated bombing of medical facilities by forces loyal to the government, and they lack sufficient oxygen tanks to treat victims.
Condemnation of the attack mounted throughout Tuesday and into Wednesday, as the US, Britain and EU blamed the Syrian government for the carnage, which took place hours before the start of a donor conference on Syria in Brussels.
Donald Trump denounced the “heinous” act that “cannot be ignored by the civilised world”, but also laid some of the responsibility on Barack Obama, saying that the attack was “a consequence of the past administration’s weakness and irresolution”. Theresa May said she was appalled by reports of the attack and called for an investigation by the Organisation for the Prohibition of Chemical Weapons.
The UK-based monitoring group the Syrian Observatory for Human Rights put the death toll in Khan Sheikhun at 72 by Wednesday morning, including 20 children.
The Syrian military said it “categorically denied” responsibility. Russia, which has heavily backed the Syrian regime, said its planes were not operating near Idlib. Early on Wednesday, the Russian defence ministry claimed a Syrian airstrike had hit a “terrorist warehouse” containing an arsenal of “toxic substances” destined for fighters in Iraq. The ministry did not state if the attack was deliberate.
Hamish de Bretton-Gordon, the director of Doctors Under Fire and a former commanding officer of the UK Chemical, Biological, Radiological and Nuclear (CBRN) Regiment, said the claim was “completely untrue”.
“No I think this [claim] is pretty fanciful, no doubt the Russians trying to protect their allies,” he told BBC Radio 4’s Today programme. “Axiomatically, if you blow up sarin, you destroy it.”
“It’s very clear it’s a sarin attack,” he said. “The view that it’s an al-Qaida or rebel stockpile of sarin that’s been blown up in an explosion, I think is completely unsustainable and completely untrue.”
Jerry Smith, the operations chief of the UN-led team that supervised the removal of Syria’s sarin stockpiles following the gas attack on the rebel-held Ghouta area of Damascus four years ago, said: “This absolutely reeks of 2013 all over again.”
In that attack, the UN said the perpetrators probably had access to the stockpile of sarin held by the Syrian military at the time, as well as the expertise to use it.
In the aftermath of the Ghouta massacre, the UN team supervised the surrender of the sarin supplies, the removal of which was supposed to have been completed early in 2014. However, suspicions remained that a portion of the stockpile was not declared to inspectors.
Khan Sheikhun is home to thousands of refugees who have fled recent fighting in the nearby province of Hama. The town is on a crossroads between Hama and Idlib and is considered vital to any regime offensive towards the northern city of Idlib.
The UN security council said it would hold an emergency meeting on Wednesday to discuss the attack, after a request from Britain and France.