The incident took place in Katanga mining area not far from Zambia and Angola, and access to the scene is difficult because of the poor state of roads in the rainy season.
The accident took place in Bojovi, about 30 km from Lobodi, in Lalapa province of the vast Katanga region, which is the size of Spain.
The train consists of 13 vehicles, including fuel containers.
"The train was on a slope and got out of its socket and fell into a hole," Okabe said. "Because of the shock, some of the fuel containers caught fire and stunned some of the passengers who were sleeping."