The team of UN Inspectors, which includes three World Health Organisation members, are making preparations to leave Syria on Saturday.
They are under pressure to make sure their findings stand up to scrutiny, and have finished taking samples from the area which was allegedly attacked with a banned toxic substance.
But the inspectors refused to accept blood collected from the deceased – custody guidelines state samples must be collected by the UN team themselves.
The 20 members have been collecting material since Monday, crossing the frontline into rebel held territory.
Meanwhile, pictures have been posted on a social media website, claiming to show people, including children, suffering after the alleged gas attack of August the 21st.
The pictures cannot be independently verified.