The nerve agent sarin was used in the April 4 chemical weapons attack against Syrian civilians that killed more than 90 people, including several children, an international chemical weapons watchdog confirmed Friday.
The attack on the rebel-held town of Khan Sheikhoun in Syria's northwestern Idlib province provoked global outcry after photos and videos of dying children surfaced in the strike's aftermath.
Though the Organisation for the Prohibition of Chemical Weapons did not identify the perpetrator, the report said the chemical likely spread from a crater in the road—a significant finding as it directly contradicts President Bashar al-Assad's version of events, the Guardian reported. Assad has claimed the mass contamination was caused after American warplanes bombed a terrorist warehouse full of poison chemicals.
"I strongly condemn this atrocity, which wholly contradicts the norms enshrined in the Chemical Weapons Convention," OPCW's director general said in a statement. "The perpetrators of this horrific attack must be held accountable for their crimes."
The report was sent to the United Nations Security Council to assist with a joint investigation to determine who was behind the attack.
The U.S. State Department reinforced its assertion that the Syrian government was behind the attack, writing in a statement Thursday night that facts published in the OPCW report "reflect a despicable and highly dangerous record of chemical weapons use by the Assad regime."
The State Department did not return a request for further comment.
British Foreign Secretary Boris Johnson said Friday he has "absolutely no doubt the finger points at the Assad regime."
"We will drive on with the UK campaign to impose sanctions on those responsible," Johnson said. "People who drop chemical weapons on innocent people should be held to account."
The report arrives several days after the White House said it had "identified preparations" for another chemical weapons attack by the Syrian government. President Donald Trump warned the Assad regime that it would "pay a heavy price" if it carried out another "mass murder attack."
Trump authorized the bombing of a Syrian airfield that took out several government jets in retaliation for the Assad regime's devastating April attack. The president did not make clear how he would retaliate if the government were to deploy a similar strike against civilians.
The United Nations and OPCW released a joint report in August 2016 blaming the Syrian government for two separate gas attacks against civilians involving the use of chlorine. Assad has denied the use of chemical weapons, claiming the attacks are staged.