With the outbreak of World War II, the role of the camp was expanded. It was used to house "undesirable" foreigners, in particular, anti-fascist intellectuals and former members of the International Brigades. After the Fall of France on 25 June 1940, it was taken over by the pro-Nazi Vichy France authorities, to house "all foreigners considered suspect or dangerous to the public order".
From 1942, Le Vernet was used as a holding centre for Jewish families awaiting deportation to Nazi labour and extermination camps. The final transport took place in June 1944 and took the remaining prisoners to Dachau concentration camp. One source says that "about 40,000 persons of 58 nationalities were interned in the camp".