Cleavage of thiamine by chlorine in tap water

We have clarified that thiamine is cleaved by residual chlorine in proportion to the rise in temperature, pH and concentration of residual chlorine. When rice was boiled in an electric rice cooker, the thiamine in the rice was cleaved by residual chlorine. It is assumed that thiamine is cleaved into hydroxymethylpyrimidine and the thiazole moiety.