You can send letters to the prisoners in the detention center, but the letters will be checked by the detention center to ensure safety.
According to "Regulations of People's Republic of China (PRC) Detention Center" and "Measures for the Implementation of Regulations of People's Republic of China (PRC) Detention Center", Article 31 The detention center may check the letters sent and received by criminals upon the entrustment of the case-handling organ. Anyone who is found to obstruct investigation, prosecution or trial may be detained and transferred to the case-handling organ for handling.
Delivery, meeting, correspondence and leave in the detention center indicate that the detention center should accept the entrustment of the case-handling organ to check the letters sent and received by detainees. After the inspection, no problem letters can be sent or given to the detainees themselves; If letters that hinder investigation, prosecution and trial are found, they shall be detained and transferred.
Extended data:
Interview with prisoners:
Article 34 correspondence between criminals and their close relatives living in China must be approved by the case-handling organ. If a prisoner requests to meet, it must be approved by the public security organ at or above the county level or the competent bureau or director of the state security organ.
Meetings and correspondence between criminals and their close relatives living in Hongkong, Macao, Taiwan Province Province and foreign countries, or between criminals of foreign nationality and their close relatives, guardians and members of embassies and consulates in China must be approved by the public security departments and bureaus of provinces, autonomous regions and municipalities directly under the Central Government or the national security departments and bureaus.
Thirty-fifth meeting with criminals shall not exceed once a month, and each meeting shall not exceed half an hour, and each meeting shall not exceed three close relatives. During the meeting, there should be case handlers and guards at the scene to monitor. Foreign criminals, ethnic minority criminals and deaf-mute criminals must also have translators hired by the case-handling organ present. During the meeting, it is forbidden to talk about the case, not to talk in code, and not to pass things privately. In violation of the provisions, do not listen to stop, shall be ordered to immediately stop the meeting.
Article 36 With the consent of the case-handling organ and the approval of the competent bureau and director of the public security organ at or above the county level, a criminal may temporarily leave his dying spouse, parents or children. Prisoners who are seriously ill and cannot return to their original places that day are not allowed to visit.
Visitors shall be accompanied and supervised by two or more investigators, and shall not spend the night outside.
References:
Measures for the implementation of the Regulations of People's Republic of China (PRC) Detention Center-Baidu Encyclopedia