An estimated 700,000 (Japanese estimation) to 2,000,000 (Chinese estimation) Japanese-produced chemical weapons were buried in China. Until 1995, Japan had refused to acknowledge that it dumped chemical weapons in the Nen River between Heilongjiang and Hulunbei'er, leaving huge amounts behind.
The Japanese National Institute for Defense Studies has a record of Japanese weapons confiscated by Kuomintang Army along with a list of the types of chemical weapons. No confiscation records about ROC / Russia have been found. However, no country has records about the locations of the buried chemical weapons. China has started gathering these abandoned weapons for destruction and burial, and they are currently buried in remote Dunhua County, in Haerbaling, Jilin (吉林) province.
The Chemical Weapons Convention
One of the focuses of the Chemical Weapons Convention was to assign responsibility for the destruction of old chemical weapons in China. The convention was signed in 1993 and according to it, all chemical weapons created after 1925 must be destroyed by the originating-country. Under the convention, Japan is building a factory in China to destroy chemical weapons.