E/CN.4/1995/31/Add.4 page 15 is apart from the wealth of information gathered and the exchange of ideas, which facilitated each side understanding the other’s position. Interviews with prisoners, the heart of the visit, were candid and marked by non-interference. 47. In camp Z-30, the only place where the selection of detainees to be interviewed could be made was at the entrance to the detention area, with one member of the Group being stationed near the door of the "political" building when the prisoners returned at the end of the day. It should be noted that, in camp A-5, the Working Group encountered none of these difficulties; prisoners were chosen by the Working Group at random to preclude any possibility of preselection; also, because of the time of day, the interviews were held outside the detention buildings, in the fields where the prisoners were working. 48. Otherwise, no obstacles were encountered. The Working Group visited the detention buildings during the day (when the prisoners were at work) and the premises used for general services (kitchens, maintenance, infirmary), and was able to speak with the prisoners and patients there. In all the camps, the solitary confinement cells were shown without hesitation. They seemed little used (in camp A-5, only for prisoners starting brawls, according to the administration; the Group noted the presence of shackles in these cells), or not used at all (in camp Z-30, the padlocks were rusted and the doors were opened only with difficulty). When asked about the infrequent use of isolation cells, camp authorities said that discipline was maintained essentially by withdrawing certain privileges, such as visits and mail, or by granting privileges, or even by public self-criticism, and by increasing the frequency or length of the visits on the basis of the degree of re-education as determined by the authorities. According to the authorities in one of the camps visited, this assessment is based on the following criteria: Good conduct; Agreement to receive instruction in civics. According to some prisoners questioned, this term really means lessons on the Communist Party and its ideals; Absence of escape attempts; Reporting to the authorities breaches of the regulations committed by other prisoners, such as planned escapes or riots. (b) Status of pre-trial detention centres 49. Each province has at least one centre exclusively for pre-trial detention. Whereas re-education and rehabilitation labour camps intended solely for serving sentences come under the Ministry of the Interior, pre-trial detention centres are run by the provincial authorities. Detainees are placed under the supervision of the public prosecutor, who is empowered to make inspections. If the prosecutor finds that an individual has been placed in detention without legal grounds, he must order his immediate release. The Working Group is not in a position, however, to ascertain what happens in practice.