TOKYO (AP) — Japanese government regulators said Wednesday that for the first time they will conduct their own investigation into the country’s nuclear crisis to address key unanswered questions.

The March 2011 earthquake and tsunami cut power and destroyed vital cooling systems at the Fukushima Dai-chi nuclear plant, causing meltdowns at three of its reactors. Several groups have already published the findings of their own investigations into the crisis, largely blaming the world’s worst nuclear disaster since Chernobyl on botched crisis management, government-industry collusion and the tsunami.