Chełmno extermination camp
On January 19, 1942, an escaped inmate from the Chełmno extermination camp, Jacob Grojanowski, reached the Warsaw Ghetto, where he gave detailed information about the camp to the Oneg Shabbat group. His report, which became known as the "Grojanowski Report", was smuggled out of the ghetto through the channels of the Polish underground, reached London and was published by June.