What is FELCYN as noted in the memoir, Marching Powder: A True Story of Friendship, Cocaine, and South America’s Strangest Jail?

FELCN is a Spanish acronym of the Bolivian federal police's special unit against drug trafficking. After Thomas is arrested, he is incarcerated by Colonel Lanza for 11 days in FELCN's jail, under terrible conditions, until his transfer to San Pedro.