International chemical weapons inspectors in Syria have been stopped from investigating two sites identified by the Syrian government as chemical weapons facilities.

The Organization for the Prohibition of Chemical Weapons (OPCW) said that verification of the other 21 chemical weapons sites have been completed. The inability for the investigators to go into the remaining two sites means that a key deadline in the mission to eliminate all the Syrian weapons has been missed.

The OPCW said that ceasefires would be necessary for their inspectors to complete their mission. The group would not say which side of the conflict was making the weapon sites too dangerous for their inspectors.

Under the United Nations resolution that authorized the inspectors to enter Syria, all chemical weapon production facilities in the nation must be destroyed by November 1st.