The document called "established rule over plant control" was conveyed in secrecy to the U.S. military base in Wonju by the U.S. Forces Command in south Korea on March 30, 1968.

It contained an order of the representative of the U.S. military advisory group on offering technological guidance and support to the puppet army to be mobilized for the work.

Also contained were the method of spraying defoliant, the method of adjusting equipment after spraying and the issue of distributing an interpreter for communication between the representative and the spraying group.

It also had records asking for not reporting the coordinates of those areas.

Meanwhile, a south Korean inhabitant, who had worked in the U.S. military base in Waegwan, Chilgok County, North Kyongsang Province for more than three decades from the late 1960s, exposed the U.S. forces' burial of defoliant on May 27, south Korean MBC said.