The Kongo peoples produce carved wooden figures, minkisi (singular: nkisi), with metal pieces embedded into the main body, which are used in various rituals to catch thieves or witches and to help solve problems of health, wealth and good fortune. Cavities in the belly and head are filled with burial relics or clay from the cemetery to bring the buried ancestors into the present, and with traditional medicines to increase their ritual power. The iron blades embedded into the figure are believed to release ancestral power. Supplementary items such as carved miniatures are attached to the outside of the figure to represent the powers of the nkisi to the outside world. The ritual involves music, dancing, sacrifices and invocations performed by the nganga, a ritual expert, who drives nails into the figure or explodes gunpowder in front of it to provoke it to action.Most of the minkisi in museums date from between 1880 and 1920. Colonial administrators tried to repress the use of minkisi, which nonetheless continues to the present day.