on 20 june 2012, tepco released its final internal investigation report. in the report, tepco complained that top politicians, including the prime minister, interfered with recovery efforts during the initial stages of the disaster by making specific requests that were out of touch with what was actually taking place at the plant. tepco concluded that the direct cause of the accident was the tsunami which knocked out the reactors' cooling system. tepco also admitted that it was at fault in not being prepared for the situation, but said that its workers did the best they could "amid unprecedented circumstances."