Head of the UN Investigation Team to probe the alleged use of chemical weapons in Syria, Ake Sellstrom, is scheduled to visit Syrian refugees in Turkey, Jordan and Lebanon, to examine cases of such use. Sellstrom has so far limited his investigative work on material presented by Western governments. He has recently visited London, Paris and Washington, where he discussed the cases with government officials there. He will now bring his investigative work to the refugee camps at the borders with Turkey, Jordan and Lebanon to probe Syrians who fled their country in search for safety and medical treatment, a senior UN diplomat said late on Wednesday. Sellstrom has been barred from visiting Syria since Secretary-General Ban Ki-moon appointed him earlier this year to look into Syrian and Western claims that government forces and the opposition used chemical weapons against each other. Ban insists that investigating material presented by Western countries is not enough and cannot substitute investigations conducted on the ground in Syria. US Ambassador Susan Rice sent a letter to Ban, last week, accusing the Syrian Government of using the nerve agent Sarin on two occasions in the northern city of Aleppo in March and April.