Vatican City ? They sat quietly on hard wooden pews, nuns in simple habits, clergymen in red-sashed cassocks, chauffeurs in sober suits, all waiting their turn to solemnly swear to keep the secrets of the papal conclave.

Housekeepers, elevator operators, waiters and other Vatican workers promised Friday never to reveal any details they might learn about the politicking and infighting that goes into the election of the pope.

No one but the 115 cardinals choosing the Roman Catholic Church’s new leader will be in the Sistine Chapel when they debate and vote during the conclave, which begins Monday afternoon. But there is a potential for Vatican workers to overhear chance remarks by cardinals between sittings.

So, with one hand on the book of the Gospels, each of several dozen Vatican officials and workers who will come in contact with the cardinals swore to keep secret anything they might learn about the conclave.

“I will observe absolute and perpetual secrecy with all who are not part of the College of Cardinal electors concerning all matters directly or indirectly related to the ballots cast and their scrutiny for the election of the Supreme Pontiff,” they intoned. “So help me God and these Holy Gospels which I touch with my hand.”

They also signed written pledges of secrecy and promised to refrain from using audio or video equipment during the closed-door votes. Violating the pledge could bring the severest of punishments the church can mete out: excommunication.

The ceremony came hours after workers scaled the roof of the Sistine Chapel and attached the chimney pipe that will spew out puffs of white smoke to announce to the world that a new pope has been elected.

Secrecy has long been a hallmark of conclaves. But the threat of leaks and spying worries officials in an age of high-tech listening devices and with some 6,000 accredited journalists prowling Vatican City in search of what 115 red-hatted “princes of the church” are thinking.

In addition, for the first time, cardinals will be allowed to move about Vatican City freely once the voting starts, though they are forbidden to talk with anyone who hasn’t been sworn to secrecy.

U.S. Cardinals Bernard Francis Law, left, and Michael Roger Mahony arrive for a Mass on Friday at the Vatican. They will participate in the conclave to elect a new pope that begins Monday.

Already, purported leaks from secret preconclave meetings are abounding in the Italian media, with newspapers reporting on the daily jockeying of factions pushing their candidates.

Early in the week, Cardinal Joseph Ratzinger was touted as the front-runner, with nearly half of the votes. By Friday, Cardinal Angelo Sodano, the No. 2 Vatican official, and Chilean Cardinal Francisco Javier Errazuriz Ossa were gaining some momentum, newspapers claimed.

The Rev. Andrew Greeley, a prominent Catholic author, said such leaks were common in the run-up to a conclave, but should dry up once the master of liturgical ceremonies cries “Extra omnes” — Latin for “all out” — and only the cardinals are left in the Sistine Chapel to vote.

“It is like the previous conclaves: About this time before they go into the conclave, the Italians begin to leak things to the Italian media and you get all kinds of wild predictions,” he said.