At least 37 suspected illegal miners have died while in the custody of the Nigeria Security and Civil Defence Corps (NSCDC) in Minna, Niger State.

Governor Mohammed Umaru Bago, who described the incident as tragic, said on Thursday that a committee had been set up to investigate the deaths and declared three days of mourning. The state police command has also launched an investigation.

The NSCDC said the victims were arrested on Tuesday and Wednesday over suspected illegal mining. Its state commandant, Suberu Siyaka Aniviye, said the agency suspected disease, but the bodies had been taken to a hospital for examination.

Preliminary intelligence, however, suggested that overcrowding and poor ventilation in the detention facility may have contributed to the deaths.

Niger State is rich in mineral resources and attracts thousands of artisanal miners, while officials and experts have linked illegal mining to criminal activities by armed groups in the state.