 Complete the following phrase:  Western officials, such as British Ambassador Mark Lyall Grant, had expressed concerns about the completeness of Syrias disclosures, and said the OPCW mission should remain in place following removal of chemical weapons until verification tasks can be completed. A late disclosure in 2014 regarding Syrias ricin program raised doubts about completeness of the governments declaration of its chemical weapons stockpile, and in early May 2015, OPCW announced that inspectors had found traces of sarin and VX nerve agent at a military research site in Syria that had not been declared previously by the Assad regime. Syria appeared to bomb Khan Shaykhun with sarin in April 2017. A 