VATICAN CITY: A book just released on the election of Pope Leo as the head of the Catholic Church last May has revealed a massive security breach during the secret conclave, in which it was discovered that one of the cardinals was carrying a cell phone.

Security officials picked up the signal of an active mobile connection just as the clerics were preparing to take their first vote inside the Vatican's Sistine Chapel.

The chapel had been fitted with jamming equipment to prevent outside communications during the secret conclave.

The cardinals looked at each other in disbelief. Then one of the older priests realized he still had a phone in his pocket and handed it over. This is described in "The Election of Pope Leo XIV," a new book by longtime Vatican reporters Gerard O'Connell and Elisabetta Piqué.

The book does not name the cardinal or suggest he kept the phone on purpose. It says he felt "confused and upset" in that moment.

The authors wrote that the scene was something "even a movie could not imagine" and that nothing like it had ever happened in modern conclaves. One such movie, Conclave, showed a complicated and dramatic papal election. But O'Connell said the real-life discovery of the phone was even more surprising than anything in the film. "Reality was better than fiction," he said.

Cardinals who take part in a conclave promise not to contact anyone outside and must give up their phones and other communication devices. The voting process can last for several days.

The Vatican press office did not respond to requests for comment about the book, which shares behind-the-scenes details of one of the world's most secret elections.

The cardinals met in a two-day conclave on May 7 and May 8 to choose a successor to Pope Francis, who died in April after leading the 1.4-billion-member Catholic Church for 12 years.

At the time, many people thought the new pope might come from Asia or Africa, since this was the most geographically diverse conclave ever, with cardinals from 70 countries. However, the book says candidates from those regions did not receive much support. The voting details come from interviews with cardinals who took part.

Although cardinals are strictly forbidden from revealing voting details without the new pope's permission, journalists often gather information from them in the years after a conclave.

According to the book, two main candidates quickly stood out. One was Italian Cardinal Pietro Parolin, a senior Vatican official widely seen as the favorite. The other was American Cardinal Robert Prevost, who was not widely known outside Church circles but later became Pope Leo XIV, the first pope from the United States.

On the first vote, held on the evening of May 7, Prevost received between 20 and 30 votes — a large number for an early round. Philippine Cardinal Luis Antonio Tagle, who had also been seen as a strong candidate before the election, received fewer than 10 votes throughout the conclave.

On the fourth vote, on the afternoon of May 8, Prevost won with 108 votes. As the final votes were being counted, Tagle was sitting next to him and even offered him a cough drop to soothe his throat, the book says.