The Fukushima nuclear crisis in Japan was a preventable disaster, according to an expert panel that investigated the worst nuclear accident in 25 years.
It says the crisis at the plant was profoundly man-made disaster which could and should have been foreseen and prevented and its effects mitigated by a more effective response.
The six-reactor Fukushima Daiichi nuclear plant was badly damaged after the 11 March 2011 earthquake and tsunami knocked out cooling systems to reactors, leading to meltdowns and the release of radioactivity.
Tens of thousands of residents were evacuated from an exclusion zone around the plant as workers battled to bring reactors under control. The plant's operator declared the reactors stable in December 2011.
The report criticised the response of plant operator Tokyo Electric Power Co (Tepco), regulators and then Prime Minister Naoto Kan.
It also blamed cultural conventions and a reluctance to question authority, Reuters reports.
The head of the inquiry said a multitude of errors left the plant unprepared for the earthquake and tsunami.
The report pointed to numerous missed opportunities to take steps to prevent the disaster, citing lobbying by the nuclear power companies as well as a "safety myth" mindset that permeated the industry and the regulatory regime as among the reasons for the failure to be prepared.
The panel found that damage from the huge earthquake, and not just the ensuing tsunami, could not be ruled out as a cause of the accident, a finding with serious potential implications as Japan seeks to bring reactors back on line.
It has urged strict checks on all reactors against guidelines set in 2006, and said Japan's 21 oldest reactors, whose construction was approved before guidelines were set in 1981, may be at similar risk from a big quake as Fukushima Daiichi.
Experts have said that an active fault may lie under Kansai Electric Power Co's Ohi plant in western Japan, whose Number 3 unit began supplying electricity to the grid on Thursday.
The investigation included 900 hours of hearings and interviews with more than 1000 people.