A bomb leftover from the Second World War was found in the grounds of a disabled power plant in northern Japan on Wednesday.
The device was found by an employee of a subcontractor working on the Fukushima Daiichii site, according to a spokesman for the company Tokyo Electric Power.
It was described as 85 centimetres long and roughly 15 centimetres in diameter, located one kilometre away from two reactor buildings.
The area where the plant is located was home to a Japanese air base subjected to bombing by US forces in the conflict, and this is believed to be the origin of the device.
The discovery prompted a perimeter to be established until the appropriate authorities could test the device, but did not disrupt work on other areas of the site.
The Fukushima power plant was heavily damaged in a major earthquake and subsequent tsunami in 2011, which led a nuclear reactor to melt down and prompted the evacuation of nearby citizens.
The plant has been disabled since, and a number of nuclear units on the site have been decommissioned in the six years after the disaster.