As we have already reported serious incident occurred in a tank dedicated to cleaning of fuel assemblies of unit two at the Paks NPP. The Paks NPP and the Hungarian Atomic Energy Authority have started independent investigation of the incident. On 11 May 2003 the Paks NPP submitted its report to the HAEA in accordance with its legally stipulated obligations. The report of the NPP consists of the following main chapters: - Short summary of the incident - Evaluation of the incident covering radiation protection, technological circumstances, activity of the staff, documentation, efficiency of self-inspections, causes of fuel damage - Non-conformities detected during the investigation, - Consequences and safety impacts of the incident - Necessary countermeasures In order to thoroughly evaluate the report the HAEA started studying it without any delay. Contrary to its routine practice the HAEA has started an independent investigation, the data collection phase of which has been completed. The results of the independent investigation will be summarised in a report and it is due by the end of May. It will also include the regulatory evaluation on the operator's report. Other main topics of the HAEA’s report will be the following: - Characteristic data of the incident - Preceding events of the incident and their evaluation - Event sequence of the incident - Process followed by the HAEA - Causes of the incident - Deviations (malfunctions) leading to the incident - Evaluation of the operator's actions in connection with the incident - Nuclear and environmental safety assessments in connection with the incident - Necessary countermeasures Both the report of the Paks NPP and the preliminary evaluation made by the authority (HAEA) show that the incident can be attributed to several independent, however, interfering causes. Further investigations are needed to reveal the fundamental technical reasons of the incident.