Tokyo Electric Power Company (Tepco) said a contract worker, aged 52, has died at the Fukushima Daiichi site in an industrial accident. The man, who worked for a company contracted by the Kajima Corporation, was cleaning and inspecting a tank on the rear of a truck when the driver is believed to have accidently closed a hatch, striking the worker on the head.

The truck was being used to transport underground water and mud dug from a frozen wall construction site to a disposal area on the Fukushima Daiichi site. Tepco said no radioactive substances were found on the man’s body. The company has launched an investigation and said it would "take measures to prevent a recurrence."

In May, Tepco was given the go-ahead to start testing a process to freeze the earth around parts of Fukushima-Daiichi, to prevent groundwater seeping into reactor buildings destroyed in the 2011 accident. A network of pipes is being injected with coolant to create a wall of frozen earth around units 1 to 4, measuring about 1.5km in length and covering some 70,000 cubic metres.

This is the third fatal accident at Fukushima Daiichi with two previous deaths recorded last January when a worker died after falling into an empty water storage tank and in March 2014 when a worker died after being buried by gravel while digging a ditch. In a separate incident last January a worker died at the Fukushima Daiini nuclear plant after equipment fell on him at a facility storing radioactive waste.

Some 7000 workers are currently involved in decommissioning Fukushima Daiichi; many of them are contract workers.