UNITED NATIONS - An international investigative panel has determined that the government of Syrian President Bashar al-Assad was responsible for a deadly sarin gas attack on April 4.
The attack on the rebel-held town of Khan Sheikhoun killed or sickened scores of civilians and led to a U.S. airstrike three days later on the Syrian military base that Washington said the regime used to launch the poison gas attack.
In their 33-page final report released to U.N. Security Council members on Thursday, a copy of which was seen by VOA, investigators from the U.N. and the Organization for the Prohibition of Chemical Weapons, a chemical weapons watchdog agency, said they examined eight possible scenarios as to how the gas was released.
They concluded that only two scenarios were likely: The sarin was released via an aerial bomb or during the explosion of an improvised explosive device.
After reviewing photographs, videos and satellite images, and taking into account eyewitness reports and forensic analysis, investigators determined that it was likely "an aerial bomb with a small explosive charge" caused the deadly incident.
The investigators said they had "sufficient credible and reliable evidence" that aircraft dropped the munitions over Khan Sheikhoun early on April 4 and that Syrian military aircraft were in the vicinity at that time. The panel said the bomb's impact caused a large crater "from which the sarin emanated."
Syria and Russia have previously suggested that the gas was released from a bomb on the ground, not the air.
The investigators did not visit the site at Khan Sheikhoun, saying it was too dangerous. Also, the crater was subsequently filled with cement, devaluing the scene.
This was the fourth confirmed case of chemical weapons use by the Assad regime.
The investigative panel also found that a second incident involving sulfur mustard in the Syrian village of Um Hosh in September 2016 was the work of Islamic State militants.
In a statement Thursday, U.S. Ambassador Nikki Haley condemned the Assad regime's repeated use of chemical weapons.
"The Security Council must send a clear message that the use of chemical weapons by anyone will not be tolerated, and must fully support the work of the impartial investigators," Haley said. "Countries that fail to do so are no better than the dictators or terrorists who use these terrible weapons."
On Tuesday, Russia used its veto to block a council resolution that would have renewed the joint investigative panel's mandate for another year. Moscow said it wanted to wait for the report's results before deciding how to proceed.
The council still has time to extend the investigators' work, as the mission does not expire until November 16.