Black smoke billowed from the chimney of the Sistine Chapel, signaling that cardinals had not come to an agreement after the first day of voting.

Surrounded by Michelangelo's imposing frescos imagining the beginning and the end of the world, cardinals locked themselves into the chapel following a final appeal for unity to heal the divisions that have been exposed by Pope Benedict XVI's shocking resignation and revelations of corruption and mismanagement in the Vatican bureaucracy. The cardinals are looking to choose a new leader for the world's 1.2 billion Catholics and their troubled church.

Led by prelates holding a crucifix and candles, the 115 scarlet-robed prelates chanted the Litany of Saints, the hypnotic Gregorian chant imploring the intercession of the saints to guide their voting, before the master of liturgical ceremonies intoned "Extra omnes" or "all out" and closed the heavy wooden doors.

Outside, thousands of people braved cold night rain and packed St. Peter's Square, eyes fixed on the narrow chimney poking out of the Sistine Chapel roof. They were rewarded some three hours after the conclave began when thick black smoke billowed out of the chimney, signaling that no pope had been elected.

The cardinals now return to the Vatican hotel for the night and resume voting Wednesday morning.

Benedict XVI's surprise resignation has thrown the church into turmoil and exposed deep divisions among cardinals grappling with whether they need a manager to clean up the Vatican's dysfunctional bureaucracy or a pastor who can inspire Catholics at a time of waning faith and growing secularism.

The leading contenders for pope have fallen into one of the two camps, with Cardinal Angelo Scola, seen as favored by those hoping to shake up the powerful Vatican bureaucracy, and Brazilian Cardinal Odilo Scherer, favored by Vatican-based insiders who have defended the status quo. Other names included Canadian Cardinal Marc Ouellet, who heads the Vatican's powerful office for bishops, and U.S. Cardinal Timothy Dolan, the exuberant archbishop of New York.

In a final appeal before the conclave began, the dean of the College of Cardinals, retired Cardinal Angelo Sodano, urged unity within the church, asking the cardinal electors to put their differences aside for the good of the church and the future pope.

"Each of us is therefore called to cooperate with the Successor of Peter, the visible foundation of such an ecclesial unity," Sodano said. He said the job of pope is to be merciful, charitable and "tirelessly promote justice and peace."

He was interrupted by applause from the pews — not so much from the cardinals — when he referred to the "beloved and venerated" Benedict XVI and his "brilliant" pontificate.

Sitting in the front row was Benedict's longtime aide, Archbishop Georg Gaenswein, who reported that Benedict was watching the proceedings from the papal residence in Castel Gandolfo, according to a Vatican spokesman the Rev. Thomas Rosica.

For over a week, the cardinals have met behind closed doors to try to figure out who among them has the stuff to be pope and what his priorities should be. But they ended the debate on Monday with questions still unanswered, and many cardinals predicting a drawn-out election that will further expose the church's divisions. The conclave proceeds in silence, with no formal debate, behind closed doors.

During the discussions, Vatican-based cardinals defended their administration against complaints that they have been indifferent to the needs of cardinals in the field. At one point on Monday, the Brazilian head of one Vatican office reportedly drew applause for challenging the Vatican No. 2, who has been blamed for most of the bureaucracy's administrative failings.

"Let us pray for the cardinals who are to elect the Roman pontiff," read one of the prayers during the Mass. "May the Lord fill them with his Holy Spirit with understanding and good counsel, wisdom and discernment."

In his final radio address before being sequestered, Dolan on Tuesday said a certain calm had taken hold over him, as if "this gentle Roman rain is a sign of the grace of the Holy Spirit coming upon us."

Based on reporting by the Associated Press.

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