Black smoke rose into the evening sky over the Vatican as a conclave of cardinals failed to select a new pope on its first vote Tuesday.

The conclave of 115 cardinals gathered in the sealed Sistine Chapel to cast ballots for who should lead the Roman Catholic Church. Who the cardinals voted for is unknown – but the black smoke means that no cardinal received two-thirds of the votes necessary.

Thousands gathered in St. Peter's Square to watch the results, but trickled quietly out of Vatican City shortly after the black smoke rose around 8 p.m. local time (3 p.m. ET).

The conclave will not vote again until Wednesday morning.

Brazilian tourist Bruno Smania was one of thousands who braved the damp weather in St. Peter's Square.

"It's a historic moment for me and for the world. I will be here all the time, waiting for the white smoke," Smania told the CBC's Karen Pauls.

Smania joined a group of Brazilians, some with their country's flags around their necks, hoping that Cardinal Odilo Pedro Scherer may become the church's leader.

Together, the group chanted "The pope from Brazil! The pope from Brazil!"

Tourists Cecilia Afione and Fernando Otero from Argentina missed the black smoke, but say they'll be back at the Vatican tomorrow.

"It's important to be here because the pope is the maximum authority," Afione said.

Secret deliberations begin with ceremony

The papal election, or conclave, began on Tuesday as the assembled cardinals staged a procession into the Sistine Chapel as they chanted the Litany of Saints — asking the saints to help them pick a new pope.

The cardinals each swore an oath to follow the selection procedure laid out by Pope John Paul II in 1996, to affirm they will be loyal and receptive to the winner, and to maintain secrecy during and after the conclave, said Father Darren Dias, an assistant professor of theology at the University of St. Michael's College in Toronto.

Monsignor Guido Marini, the master of papal liturgical ceremonies, then gave the order extra omnes — "everyone out" — and all but those taking part in the conclave were to leave the chapel's frescoed walls. The chapel's heavy doors were then shut.

Wednesday smoke guide Black smoke billows from the Sistine Chapel chimney on Tuesday. (Dylan Martinez/Reuters) The conclave is set to vote four more times on Wednesday, twice in the morning and twice again in the afternoon. If a pope is picked, white smoke will rise from the Sistine Chapel's chimney. If not, ballots are burned in pairs, meaning there will be two more blasts of black smoke if the cardinals can't elect a pope.

The day began with the dean of the College of Cardinals, Angelo Sodano, leading the celebration of the Pro eligendo Pontificiemass — the mass for the election of a pope — inside St. Peter's Basilica, joined by voting cardinals.

Sodano, in his homily, issued an appeal for church unity, aimed squarely at the cardinals heading into a papal election that has no clear front-runner.

"Each of us is therefore called to co-operate with the Successor of Peter, the visible foundation of such an ecclesial unity," Sodano said.

There was applause when Sodano mentioned the "beloved and venerated" Pope Benedict XVI, whose retirement last month set in motion the events of the conclave.

Before the conclave, cardinals met 10 times to discuss the decision and issues the church is facing. Although the meetings are held behind closed doors, Vatican spokesman Rev. Federico Lombardi revealed the cardinals debated their expectations for the next pope and what his role should be.

Decision was unlikely on first vote

The chances of the conclave selecting a new pope on its first vote was highly unlikely. For a winner to be declared, he must receive two-thirds of the vote — 77 votes in total.

The cardinals will now hold up to four votes per day in secret sessions in the chapel until Benedict XVI's successor is chosen.

When they are not in the chapel, the cardinals will remain within Vatican walls, staying at Casa St. Martha, a hotel that was built while John Paul II was pope. The cardinals will eat and sleep at the hotel, isolated from the outside world for the duration of the conclave.

Anyone interacting with the cardinals during the conclave — such as doctors, confessors, maids or bus drivers — swore an oath of secrecy Tuesday. If they break the oath, they will face ex-communication by the church.

No clear front-runner

It's not clear how long the conclave will take. John Paul II was elected after a two-day conclave. Benedict was elected after two days, and four ballots.

Once the 115 cardinals — all under the age of 80 — have made their decision, the selected cardinal will be asked whether or not he accepts the position. More than one cardinal has previously refused the papacy, though not in recent history. If he accepts, he immediately becomes pope and must select a new name.

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As of late Monday, there appeared to be no clear leading candidate, but many different names have been floated as people try to determine who will be selected.

Canada's Cardinal Marc Ouellet is viewed by many to be among the leading contenders. Several other non-European candidates, including Cardinal Odilo Pedro Scherer, 63, of Brazil and Cardinal Peter Turkson, 64, of Ghana, have also been mentioned as possible contenders for a job that has never been held by a non-European.

"The debate will be about priorities, and what the most urgent issues are," Vatican analyst David Perlich told CBC News Network on Monday as final preparations for the conclave were underway.

Perlich said there are about 10 men who stand a "really good opportunity" of being elected, but he noted that there have been surprises in the past, including Karol Józef Wojtyła, who was elected in 1978 and served as Pope John Paul II until he died in 2005.

Father Terence Fay, of the University of Toronto School of Theology, said the cardinals will be looking for someone who they believe has the "charism," or spiritual grace, to carry the burden of the papacy.

Cardinals to negotiate outside Sistine Chapel

Papal historian Michael Walsh said discussions among the cardinals about who should be elected pope take place outside of the Sistine Chapel, at their hotel and over meals.

"The cardinals may have to do a bit of horse-trading … before somebody can muster the two-thirds majority [required to be elected pope]," he told CBC News, speaking from London.

Dias said he was excited by the possibility that the next pope could be a non-European. He said that is a "real possibility," as many of the cardinals viewed as the leading contenders are not from Europe.

"I think that is pretty exciting for the church," he told CBC's Suhanna Meharchand.

The direction the new pope will give the church, which has recently been plagued with multiple scandals, will be important. Over the past few years, reports of sexual abuse by senior clergy have emerged, Vatican finances have been under scrutiny, and sensitive Vatican documents were leaked, raising questions about the church's ability to thrive in the digital age.

The current conclave comes after Benedict retired in late February, the first pope to do so in nearly 600 years.

Benedict, who was elected pope in 2005, has promised "unconditional reverence" and obedience to the new pope as he lives out his retirement at a monastery within the Vatican.