In October 1946, several mass graves were exhumed in the forests of Piaśnica. The exhumation was organized by two commissions: the Exhumation Commission, established by the Wejherowo branch of the Polish Western Union (PZZ) in Wejherowo under the leadership of Leon Prusiński, and the Forensic Commission, chaired by Judge Antoni Zachariasiewicz, who was the chairman of the District Commission for the Investigation of German Crimes in Gdańsk.
During the work, 27 graves were examined. Two of them contained 305 bodies, which were recovered and laid out among the trees so that interested families could identify them. The exhumation report, which was forwarded to the Main Commission for the Investigation of German Crimes in Poland, listed 55 bodies of victims who had been identified by their relatives. This is how the first list of victims of the Nazi crime in Piaśnica was created.
Ten years later, this list was published by Władysław Sasinowski in his study Piaśnica 1939-1944, which was published in 1956 by the Committee for the Construction of a Memorial to the Victims of Piaśnica in Wejherowo.
In addition, the author published a list of 225 names of people from the former Gdańsk Voivodeship who were probably murdered in the Piaśnica Forest between 1939 and 1940, compiled based on witness statements and questionnaires on war losses from the files of the former (dissolved by the authorities in 1950) department of the Polish Western Union in Wejherowo. Sasinowski added a comment to the list, pointing out that due to a lack of evidence, it contains only a small portion of the names that could be identified and may contain inaccurate personal data. The list of 225 people does not include (apart from 9 names) the 55 people mentioned above who were identified during the exhumation. In total, Władysław Sasinowski named 271 victims of the Nazi crime in Piaśnica on the published list of 55 people who had been identified by their families in 1946 and on the list of 216 people who had been identified based on questionnaires and witness statements.