Real Inferno for Dan Brown translators who toil in underground bunker to decode his latest book

Even Dante could not have conjured quite such a hellish punishment: for almost two months, 11 people were confined to an underground bunker in Italy and forced to read the new novel by Dan Brown – all day, every day. Brown's Inferno, which reportedly makes repeated reference to Dante's Inferno, is due for publication on 14 May.

Its publishers were so keen to see the book released in several languages simultaneously that they hired 11 translators from France, Spain, Germany, Brazil and Italy to translate it intensively between February and April 2012. The translators are said to have worked seven days a week until at least 8pm, in a windowless, high-security basement at the Milan headquarters of Mondadori, Italy's largest publishing firm.

The 11 were forbidden from taking mobile phones into the bunker, which was guarded by armed security personnel. Their laptops were screwed to the workstations, and they were allowed access to the internet only via a single, supervised, communal computer.

Although the translators were permitted to eat meals at the Mondadori staff canteen, they were each given cover stories to conceal the true purpose of their work. When not in use, the manuscripts were stored in safes.

Foreign translations of English-language bestsellers tend to be published after the originals, and their publishers lose sales as a result. According to the blog Love German Books, the German version of Brown's last novel, The Lost Symbol, was released a month after its English original, which had already reached No 2 on the country's fiction bestseller list. Inferno, by contrast, will be published simultaneously in English, French, German, Spanish, Catalan, Italian and Portuguese.

Its translators, however, were plainly not trusted not to pirate the text before 14 May. Not only were they ordered never to discuss its plot, but they were also told to sign in and out each time they entered or left the bunker – and even to keep a log of their activities, which reportedly included entries such as "cigarette break", "short walk" and "meal".

For translators accustomed to working at home alone, it was an unusual experience, according to TV Sorrisi e Canzoni, a weekly magazine also published by Mondadori, which is owned by the Berlusconi family. Annamaria Raffo, one of three Italian translators, told the title that there was "reserve, even distrust" among the group at first, but by the end of the process the bunker had "a playground atmosphere".

According to the French translator Carole Delporte, "The bunker experience allowed us to immerse ourselves completely in Dan Brown's book."

Inferno is the fourth of Brown's mystery thrillers to feature the Harvard symbology professor Robert Langdon, who is described in The Da Vinci Code as looking "like Harrison Ford in Harris tweed", yet was played by Tom Hanks in the film versions of that book and its predecessor, Angels and Demons. The Amazon description for the new novel reveals: "In the heart of Italy, Robert Langdon is drawn into a harrowing world centred on one of history's most enduring and mysterious literary masterpieces... Dante's Inferno. Against this backdrop, Langdon battles a chilling adversary and grapples with an ingenious riddle that pulls him into a landscape of classic art, secret passageways, and futuristic science."

Substitute Dante for Da Vinci and Italy for France, and you have the plot of The Da Vinci Code, a formula Brown also followed closely for his other Langdon bestsellers.

It is a narrative that has served him well: a 2011 crime writers rich list compiled by the digital TV crime channel Alibi estimated his fortune at $400m (£257m), second only to John Grisham, with $600m. The 48-year-old New Hampshire native, who studied creative writing in the same class as the late David Foster Wallace at Amherst College in Massachusetts, has seen his previous books translated into 52 languages.

As of 2012, they had sold more than 200 million copies combined, while the two Tom Hanks film adaptations have grossed approximately $1.25bn between them. In an interview before the publication of The Lost Symbol, Brown said he had ideas for "about 12" more Langdon books.

Is that a promise or a threat?