On 13 September 2018, the Mexican authorities initiated an anti-circumvention investigation on imports of slightly modified ammonium sulfate from China. This investigation follows suspicion that the definitive antidumping duty imposed in October 2015 on imports of ammonium sulfate from China might be circumvented (see related intervention). The products subject to investigation are classified under the following HS code subheading: 3105.90.99. The investigation follows the application lodged on 30 May 2018 by Agrogen, S.A. de C.V. and Metalúrgica Met-Mex Peñoles, S.A. de C.V.

On 8 June 2019, the Mexican authorities extended the antidumping duty imposed on imports of ammonium sulfate from China (see related intervention) to imports of slightly modified ammonium sulfate from China following the conclusion of an anti-circumvention investigation. The rate of duty is USD 0.0929 or 0.1703 per kg depending on the company. The resolution extending the definitive duty was issued on 7 June 2019.

On 10 September 2020, the Mexican authorities initiated a sunset review following the application lodged by 12 September 2020 by Agrogen, S.A. de C.V. The sunset review covers both the original imposed definitive duty (see related intervention) and the above-extended duty following the conclusion of an anti-circumvention investigation.