About 100 liters of kerosene leaked from a construction site for the Hokkaido Shinkansen's Futatsumori Tunnel in Kutchan, Hokkaido, and flowed into the nearby Takami River, the Japan Railway Construction, Transport and Technology Agency said on the 6th.
According to the agency, a tank being brought in by crane tipped over at around 4:25 p.m. on the 5th, and the kerosene ran out through a drainage pipe into the river. Workers have set up oil fences and absorbent mats and are recovering the fuel.
The kerosene is used as fuel to keep concrete at a temperature that stops it from cracking before it sets, the agency said. Kutchan town officials said the river water is not used for drinking.
The agency is investigating how and why the tank fell.