Story highlights Black smoke comes from the chapel chimney, meaning no winner in first vote

With the cardinals inside, the doors to the Sistine Chapel close as the conclave starts

Cardinal Angelo Sodano calls for love, unity and cooperation with the next pontiff

The 115 cardinals will cast ballots for the new spiritual leader of the Roman Catholic Church

Black smoke billowed from the chimney of the Sistine Chapel Tuesday night, indicating that cardinals gathered at the Vatican to elect a new pope had not chosen one in the first ballot of their conclave.

The start of the secret election got underway earlier in the day, as the heavy wooden doors to the chapel swung closed on the 115 Roman Catholic cardinals charged with selecting the next pontiff.

The next round of voting will begin Wednesday morning. Results will be revealed by puffs of smoke from the chimney following each ballot.

Black smoke, no pope. White smoke, success.

On a day rich with symbolism, the scarlet-clad cardinals entered the Sistine Chapel in solemn procession, chanting prayers and watched over by the paintings of Renaissance artist Michelangelo.

Led by the conclave's senior cardinal, Giovanni Battista Re, each of the cardinal-electors -- those under age 80 who are eligible to vote -- then swore an oath of secrecy.

Photos: Photos: Vatican prepares to choose a pope Photos: Photos: Vatican prepares to choose a pope Vatican prepares to choose a pope – Pope Francis, the Argentinian Cardinal Jorge Mario Bergoglio, appears on the St. Peter's Basilica's balcony after being elected the 266th pope of the Roman Catholic Church on Wednesday, March 13, at the Vatican. Hide Caption 1 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – White smoke billowing from the Sistine Chapel signals a new pope has been chosen on Wednesday, March 13. The 115 cardinal-electors, meeting in strict secrecy, needed to reach a two-thirds plus one vote to elect the 266th pontiff. Hide Caption 2 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – A woman looks to the chimney of the Sistine Chapel on St. Peter's Square, waiting for the smoke on March 13. Hide Caption 3 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Black smoke billows from the chimney, indicating that the College of Cardinals has failed to elect a new pope on March 13. Hide Caption 4 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – A woman prays while she waits for the selection of a new pope on March 13. Hide Caption 5 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – A nun waits for the results at the Vatican on March 13. Hide Caption 6 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – People use flags as shelter from the rain on March 13 in Vatican City. Hide Caption 7 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – A seagull stands on a statue of St. Peter as Catholics and other observers await the results on March 13. Hide Caption 8 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – People wait under umbrellas for the College of Cardinals to elect a new pope. Hide Caption 9 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – A seagull perches on a statue in St. Peter's Square on March 13. Hide Caption 10 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – People shelter under umbrellas while they wait in St. Peter's Square for news on the election of a new pope on March 13 in Vatican City. Hide Caption 11 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Crowds gather in St. Peter's Square on the second day of the conclave on March 13. Hide Caption 12 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Cardinals attend the religious Mass Pro Eligendo Romano Pontifice at St. Peter's Basilica in the Vatican, Vatican City, on March 12. The Catholic Church's 115 cardinal electors are taking part in the Mass ahead of entering the conclave for a papal election that observers say has no clear favorite. Hide Caption 13 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – A pilgrim prays in St. Peter's Square as cardinals attend mass before entering the conclave on March 12, in Vatican City, Vatican.

Hide Caption 14 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – A few pilgrims are present in St. Peter's Square as night falls on Monday, March 11. Hide Caption 15 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – St. Peter's Basilica is seen at sunset on the eve of the conclave on March 11. Hide Caption 16 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Nigerian Cardinal John Onaiyekan is surrounded by media on March 11 as he leaves the final congregation before cardinals enter the conclave to vote for a new pope. Hide Caption 17 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Canadian Cardinal Marc Ouellet is photographed by media as he leaves the final congregation on March 11. Hide Caption 18 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Fernando Canini, administrator of the Museo delle Cere (wax museum), prepares the figure of Pope Benedict XVI at the museum on March 11 in Rome. Hide Caption 19 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Tourists take in the view from the cupola on St. Peter's Basilica on March 10. Hide Caption 20 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – People gather at St. Peter's Square at the Vatican on Sunday, March 10, ahead of the cardinals' conclave. Hide Caption 21 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Nuns pray inside St. Peter's Basilica on March 10. Hide Caption 22 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Priests pray in front of St. Peter's Basilica at the Vatican on Saturday, March 9. Hide Caption 23 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Vatican City firefighters set up the chimney on the roof of the Sistine Chapel on March 9 ahead of the papal conclave. Hide Caption 24 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Vatican workers made final preparations on the Sistine Chapel on March 9. Hide Caption 25 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Members of the Vatican Fire Brigade install the chimney on top of the Sistine Chapel on March 9. Hide Caption 26 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Workers set up inside the Sistine Chapel as preparations begin before the papal conclave on March 9. Hide Caption 27 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – The sun sets over St Peter's Basilica as cardinals prepare to vote for a new pope on March 9. Hide Caption 28 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – French Cardinal Philippe Barbarin greets colleagues as he arrives for a pre-conclave meeting on Saturday, March 9. Hide Caption 29 of 36 Photos: Photos: Vatican prepares to choose a pope Photos: Vatican prepares to choose a pope – The stoves that will signal the outcome of papal voting are installed inside the Sistine Chapel at the Vatican on March 8. Hide Caption 30 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Italian Cardinals Angelo Scola (left) and Ennio Antonelli arrive for a pre-conclave meeting on Friday, March 8. Hide Caption 31 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Cardinal Peter Kodwo Appiah Turkson of Ghana arrives at the Vatican on March 8. Hide Caption 32 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Cardinal Ruben Salazar Gomez of Colombia arrives for a meeting on March 9. Hide Caption 33 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Cardinal Timothy Michael Dolan of the United States arrives for a meeting on March 9. Hide Caption 34 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Cardinals Odilo Scherrer (left) of Brazil and Geraldo Agnelo of Italy arrive for a meeting at the Vatican on March 9. Hide Caption 35 of 36 Photos: Photos: Vatican prepares to choose a pope Vatican chooses a new pope – Two painters prepare the walls of the Sistine Chapel on Friday, March 8 in advance of the papal conclave. Hide Caption 36 of 36

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A designated official then gave the order, in Latin, to those not authorized to remain, "Extra omnes" -- that is, "Everyone out."

With all those not taking part in the conclave gone, the cardinals will remain locked in isolation until one candidate garners two-thirds of their votes.

That man will emerge from the process as the new spiritual leader of the world's 1.2 billion Roman Catholics.

Huddled under umbrellas as rain came down, crowds of onlookers watched on big screens set up in St. Peter's Square until the doors to the Sistine Chapel were shut.

'Noble mission'

Earlier, the cardinals celebrated a morning Mass at St. Peter's Basilica, where they prayed for guidance in making a choice that could be crucial to the direction of a church rocked by scandal in recent years.

Applause echoed around St. Peter's as Cardinal Angelo Sodano, dean of the College of Cardinals, offered thanks for the "brilliant pontificate" of Benedict XVI, whose unexpected resignation precipitated the selection of a new pope.

Sodano's homily focused on a message of love and unity, calling on all to cooperate with the new pontiff in the service of the church.

"My brothers, let us pray that the Lord will grant us a pontiff who will embrace this noble mission with a generous heart," he concluded.

Members of the public had waited in long lines Tuesday morning to join the Mass. As the service began, the morning sunshine came to an abrupt end, with the skies letting loose thunder, lightning and a torrential downpour.

Before the service, the cardinal-electors had moved into Casa Santa Marta, their residence at the Vatican for the duration of the conclave.

Jamming devices have been put in place to stop them from communicating with the outside world via mobile phones or other electronic means as they make their decision.

Rome is abuzz

Rome was abuzz Monday with preparations for the conclave , from the 5,600 journalists the Vatican said had been accredited to cover the event to the red curtains unfurled from the central balcony at St. Peter's, the spot where the world will meet the new pope once he is elected.

Tailors have completed sets of clothes for the new pope to wear as soon as he is elected, in three sizes.

Video released by the Vatican over the weekend showed the installation of a pair of stoves inside the chapel. One is used to burn the cardinals' ballots after they are cast and the other to send up the smoke signal -- the one that alerts the world that a vote has been taken and whether there's a new pope.

Workers scaled the roof of the chapel Saturday to install the chimneys

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When cardinals elected Benedict in 2005, the white smoke signaling the decision came about six hours after an earlier, inconclusive vote, Lombardi said.

It took another 50 minutes for Benedict to dress, pray and finally appear on the balcony of St. Peter's, he said.

The longest conclave held since the turn of the 20th century lasted five days.

On Monday, cardinals held the last of several days of meetings, known as General Congregations, to discuss church affairs and get acquainted. Lombardi said 152 cardinals were on hand for the final meeting.

As well as getting to know their counterparts from around the world, the cardinals discussed the major issues facing the church, including its handling of allegations of child sex abuse by priests and a scandal over leaks from the Vatican last year that revealed claims of corruption, as well as the church's future direction.

Church rules prevent cardinals over the age of 80 from participating in the conclave but allow them to attend the meetings that precede the vote.

Who will be chosen?

Meanwhile, the Italian news media are full of speculation about which cardinal may win enough support from his counterparts to be elected, and what regional alliances are being formed.

According to CNN Vatican analyst John Allen, also a correspondent for the National Catholic Reporter, the race was wide open as the cardinals entered the conclave.

Unlike in 2005, when Benedict XVI was believed to be the favorite going into the election, no one has emerged as a clear frontrunner this time around, Allen said.

Some names have cropped up in media reports as possible contenders, however. They include Italy's Cardinal Angelo Scola; Brazil's Odilo Scherer; Marc Ouellet of Quebec, Canada; U.S. cardinals Sean O'Malley of Boston and Timothy Dolan of New York; and Ghana's Peter Turkson.

A mobile phone survey of 20,000 Africans from 11 nations, conducted by CNN in conjunction with crowd sourcing company Jana, found that 86% thought an African pope would increase support for Catholicism in Africa.

Italy potentially wields the most power within the conclave, with 28 of the 115 votes, making it the largest bloc in the College of Cardinals. The United States is second with 11. Altogether, 48 countries are represented among the cardinal-electors.

"Many would say it's all about politics at this point," Monsignor Rick Hilgartner, head of U.S. Conference of Catholic Bishops Secretariat on Divine Worship, told CNN, "but I think it's important to remember that they also recognize that this is a very spiritual moment."

Once the doors close and the conclave begins, he says, it's less about politicking and "more about prayer as they each in silence write their votes."

Sixty-seven of the cardinal-electors were appointed by Benedict, who stepped down at the end of last month, becoming the first pontiff to do so in six centuries.