When, in the context of cooperation with the authorities of other Member States of the European Union exercising powers similar to its own or with the European authorities mentioned in 9° of I of Article L. 821-1, a request for information, documents or assistance is made to the High Council by one of these authorities, its chairman shall without delay take the necessary measures to collect the information and documents or to carry out the control operations that are the subject of the request. Subject to the provisions of Article R. 821-17, the information gathered shall be communicated without delay to the requesting authority, as the case may be, by the Chairman or by the General Rapporteur. If the chairman of the High Council or, where applicable, the general rapporteur, is unable to attend, he shall inform the requesting authority without delay, specifying the nature of the difficulties encountered.