Taken from an Allied intelligence report on POW Camps and conditions on Formosa compiled in October 1945.
The Kinkaseki Copper Mine had the largest output of copper in the Japanese Empire. It was a commercial enterprise, although run along military lines - with the foremen and staff wearing insignia denoting seniority or rank. The main mine head was situated one mile from the Kinkaseki Prisoner-of-War Camp.
Although mining conditions universally are severe, it is to be emphasized that few can equal the hazards of this mine. There was no lighting in the mine - the prisoners used carbide lamps, no props in the shafts - rock falls were a daily occurrence, and down the steps there ran a stream of sulphurous, acid water. Passage through the tunnel, made twice daily by the POWs, constituted a severe mental strain, and a physical risk. In their unfed condition, and often too ill to work - in the opinion of the Senior Medical Officer of the POWs, the trials of this tunnel alone brought extreme suffering to the men.
There was no ventilating system whatsoever in the mine. Heat and humidity were intense throughout, but at the greatest depth, where the Chinese labourers refused to work, British prisoners were forced to.
Conditions were so extreme that many prisoners collapsed while digging in the chutes and had to be revived by their comrades. The temperatures at the lowest level ranged from 130 degrees F, and the sulphurous water - in which the POWs often had to stand while working - often exceeded this. Many men experienced a delayed asphyxiation owing to the lack of oxygen in the non-ventilated tunnels. In the very worst of the chutes, of the comparatively fit men, none could work for more than minutes without collapsing.
Throughout (most of) the course of the POWs' use in the mine, no medical attention was permitted in the mine. Ranging from light injuries, collapses of the sick and mal-nourished, to the maimed or killed in the mine - all were without medical relief until the camp was reached later in the day at 1800 hours.
Early departure from the mine was forbidden, no matter what the reason.
Bearing in mind the despatch to work of men so ill they had to be helped to the mine, and their inevitable collapse in the lower depths, and their journey up the almost perpendicular shaft back to the mine's main tunnel, and thence by tunnel to the camp, the ordeal was the ultimate in brutality!