In December 2019 "Le Monde" reported that the joint effort by British, Swiss, French and U.S. intelligence agencies had discovered an apparent "rear base" of GRU in southeastern France, which was presumably used by GRU for the clandestine operations carried out throughout Europe. Investigators had identified 15 agents — all of them members of GRU's Unit 29155 — who visited Haute-Savoie in the Auvergne-Rhône-Alpes, region of France from 2014 to 2018, including Alexander Petrov and Ruslan Boshirov, who are believed to be behind the poisoning of the former GRU colonel and British double agent Sergei Skripal in Salisbury in 2018.