The Auschwitz III-Monowitz camp was established in October 1942 on the site of the displaced and expelled Polish village of Monowice, located 6 km from the Auschwitz I camp. It was connected with the construction of the synthetic rubber and fuel plant by a German chemical company IG Farbenindustrie.
Dr. Piotr Setkiewicz, head of the Memorial Research Center, talks about the history of the third part of the Auschwitz camp complex.

You can also listen to "On Auschwitz" (4) that explains the role of the German company IG Farbenindustrie in the expansion of Auschwitz, creation of Birkenau & why in March 1942 the concentration camp became also an extermination center for Jewish people: https://anchor.fm/auschwitz-memorial/episodes/On-Auschwitz-4-Transformation-of-Auschwitz-concentration-camp-into-an-extermination-center-e13bat2