Japan's nuclear regulator says it plans to restart a probe into the causes of the Fukushima Daiichi nuclear accident as decontamination at the site edges ahead.
The Nuclear Regulation Authority suspended the probe after compiling an interim report in 2014. High levels of radiation in the plant hampered further investigation.
NRA Chairman Toyoshi Fuketa revealed the restart plan on Wednesday. He said cleanup work has led to an increase in areas with lowered radiation levels, and that the progress of decommissioning work has improved access to unknown data in reactor buildings.
The regulator hopes to examine equipment designed to release gas from a containment vessel to lower pressure inside, to find out why a massive amount of radioactive gas was discharged in the accident.
The NRA plans to issue a report in 2020.
Fuketa said investigators will find more to study as the situation improves. He added that he will realign his team to address new developments.