Each was given an alibi and cover story to offer to anyone who showed too much curiosity about what they were doing all day down in the bunker.
The extraordinary security measures and the translators' strange experience were revealed in an Italian magazine, TV Sorrisi e Canzoni, which is owned by Mondadori.
Carole Del Port, a French translator, said: "The time outside the bunker was essentially reduced to nothing - lunch, dinner at a very late hour and sleep.
"But it was a unique, fantastic experience - a rare opportunity to work in a group for weeks and to experience total immersion in the world of Dan Brown."
One translator joked: "I'm not allowed to tell you anything about it. If I did I'd have to shoot you."
Brown's Inferno
Inferno is the latest book by Dan Brown to feature his hero, Harvard "symbology" expert Robert Langdon, who was played by Tom Hanks in the film versions of The Da Vinci Code and Angels and Demons.
In an Amazon entry the plot is summarised: "Robert Langdon, is drawn into a harrowing world centred on one of history's most enduring and mysterious literary masterpieces.
Drawing from Dante's poem, Langdon races to find answers and decide whom to trust ... before the world is irrevocably altered."