In a high profile ruling, the Tokyo District Court said the former chairman of Tokyo Electric Power Company Holdings, Tsunehisa Katsumata, and three other former executives failed to fulfil their duty of taking the utmost safety precautions despite knowing the risks of a serious accident in case of a major tsunami. It said they could have prevented the disaster if they had taken available scientific data more seriously and acted sooner. A magnitude 9.0 earthquake and tsunami destroyed key cooling systems at the Fukushima Daiichi plant, causing its three reactors to melt down, spreading massive radiation in the area and keeping tens of thousands of residents from returning home due to radioactive contamination and safety concerns.