Geneva Convention (IV): Relative to the Protection of Civilian Persons, Part III, Section 4, Chapter XI
The wills of internees shall be received for safe-keeping by the responsible authorities; and in the event of the death of an internee his will shall be transmitted without delay to a person whom he has previously designated.
Deaths of internees shall be certified in every case by a doctor, and a death certificate shall be made out, showing the causes of death and the conditions under which it occurred.
An official record of the death, duly registered, shall be drawn up in accordance with the procedure relating thereto in force in the territory where the place of internment is situated, and a duly certified copy of such record shall be transmitted without delay to the Protecting Power as well as to the Central Agency referred to in Article 140.
The detaining authorities shall ensure that internees who die while interned are honourably buried, if possible according to the rites of the religion to which they belonged, and that their graves are respected, properly maintained, and marked in such a way that they can always be recognized.
Deceased internees shall be buried in individual graves unless unavoidable circumstances require the use of collective graves. Bodies may be' cremated only for imperative reasons of hygiene, on account of the religion of the deceased or in accordance with his expressed wish to this effect. In case of cremation, the fact shall be stated and the reasons given in the death certificate of the deceased. The ashes shall be retained for safe-keeping by the detaining authorities and shall be transferred as soon as possible to the next of kin on their request.
As soon as circumstances permit, and not later than the close of hostilities, the Detaining Power shall forward lists of graves of deceased internees to the Powers on whom the deceased internees depended, through the Information Bureaux provided for in Article 136. Such lists shall include all particulars necessary for the identification of the deceased internees, as well as the exact location of their graves.
Every death or serious injury of an internee, caused or suspected to have been caused by a sentry, another internee or any other person, as well as any death the cause of which is unknown, shall be immediately followed by an official enquiry by the Detaining Power.
A communication on this subject shall be sent immediately to the Projecting Power. The evidence of any witnesses shall be taken, and a report including such evidence shall be prepared and forwarded to the said Protecting power.
If the enquiry indicates the guilt of one or more persons, the Detaining Power shall take all necessary steps to ensure the prosecution of the person or persons responsible.