UN investigators will this week travel to an air base in Syria that the United States and its allies say was used to launch a sarin gas attack on Khan Sheikhoun, diplomats told AFP on Wednesday. The trip to the Shayrat airfield comes just weeks before the release of a much-awaited report on the Khan Sheikhoun attack that the West and a UN commission have said was carried out by Assad’s terrorists. The team from the joint UN-OPCW (Organisation for the Prohibition of Chemical Weapons) probe, known as the JIM, left on Monday for Damascus and is to go to the Shayrat airbase, said a Security Council diplomat, who asked not to be identified. The United States in April launched a missile attack on Shayrat in a quick response to Assad sarin gas attack, whose warplanes had departed from that airfield to Khan Sheikhoun. At least 87 people, including more than 30 children, died in the gas attack on 4 April. The JIM visit to Shayrat will address criticism from Russia that the panel is biased because it declined to accept Assad regime’s offer to visit the military base. The joint investigation of the United Nations and the OPCW was set up in 2015 by the Security Council to determine who is behind chemical weapons use in Syria. The JIM has already determined that Assad terrorists were responsible for chlorine attacks on three villages in 2014 and 2015, and that ISIS terrorists used mustard gas in 2015.