 However, the camp's authorities stopped formally registering detainees in September 1939, after mass arrests began.According to incomplete data from Soviet sources, at least 10,000 people had gone through the prison.Prisoners included members of the Organization of Ukrainian Nationalists (OUN), Polish Communist Party (KPP) and National Radical Camp (ONR), as well as members of the People's Party (SL) and Polish Socialist Party (PPS).