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The cardinals participating in the conclave have now retired for the evening to Santa Marta, a building adjacent to St. Peter’s Basilica, where the Vatican guesthouses are located.

They will return to the Sistine Chapel for the first full day of the conclave on Thursday morning.

On Day 2, the cardinals will begin their day with a mass in the Pauline Chapel and then retreat to the Sistine Chapel for voting. They will participate in four rounds of voting, with two burnings of the ballots planned, one in the morning and one in the evening.

Voting will continue until they reach a two-thirds majority to elect a new pope.

-ABC News' Clark Bentson and Phoebe Natanson

The first day of voting at the papal conclave has concluded.

Black smoke emerged from the Sistine Chapel, signifying that the next pope has not yet been elected.

A crowd of more than 30,000 cheered as the first round of smoke from the conclave appeared.

When white smoke emanates from the chimney, it will mean the next leader of the Catholic Church has been chosen.

The conclave will commence for a second day of voting on Thursday.

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Black smoke from Sistine Chapel — papal conclave yields no new popeBlack smoke billows over the Sistine Chapel, signaling a new pope has not been elected.

ABCNews.com

A new pope could be elected as soon as the first ballot on Wednesday, or the process could continue for days. Since 1831, no conclave has lasted more than four days.

Up to four rounds of voting typically take place in a day. If no clear choice has emerged after three days, balloting is suspended for 24 hours to allow cardinal electors time to reflect. Another seven rounds of balloting then takes place, followed by another break, and so on.

If no pope is elected after 33 or 34 votes -- generally about 13 days -- then a new rule introduced by Pope Benedict XVI decrees the two leading candidates as determined by previous ballots will engage in a runoff vote. If the candidates are members of the conclave, they cannot vote in the runoff but are present for it. Whichever candidate receives the necessary two-thirds majority of the votes is the new pope.

Cardinal Jean-Paul Vesco, the archbishop of Algiers, told ABC News it would be "unexpected" if the conclave goes past Friday.

More than 30,000 people have gathered in Vatican Square for a glimpse of the smoke expected to emanate from the chimney of the Sistine Chapel following the official start of the papal conclave.

Black smoke would indicate that a pope has not yet been elected. White smoke signifies that one of the 133 cardinals has secured two-thirds of the votes to become the next pope.

It is unlikely that a new pope will be elected on the first day of voting.