A sequence of explosions occurred in an ammunition factory in Novaky, Slovakia, on 2 March 2007 and caused a major industrial accident. The origin times and number of explosions were key aspects for the state investigation team to explain the primary cause and development of the accident. An analysis of seismic records was the only way to determine reliable origin times. We were able to identify the two strongest explosions directly from the seismic records. Detailed time-frequency analysis enabled us to identify acoustic waves caused by the explosions. This led to the subsequent identification of two weaker explosions in seismic records and an indication of two even weaker explosions that could not be identified in the records. The seismic analysis is supported by results of the onsite investigation by the state investigation team.