Using gas vans, Chełmno had its roots in the Aktion T4 euthanasia program. Majdanek began as a POW camp, but in August 1942 it had gas chambers installed. A few other camps are occasionally named as extermination camps, but there is no scholarly agreement on the additional camps; commonly mentioned are Mauthausen in Austria and Stutthof. There may also have been plans for camps at Mogilev and Lvov.
Bergen-Belsen [ˈbɛʁɡn̩.bɛlsn̩], or Belsen, was a Nazi concentration camp in what is today Lower Saxony in northern Germany, southwest of the town of Bergen near Celle. Originally established as a prisoner of war camp, in 1943, parts of it became a concentration camp. Initially this was an "exchange camp", where Jewish hostages were held with the intention of exchanging them for German prisoners of war held overseas. The camp was later expanded to accommodate Jews from other concentration camps.