But the 115 Roman Catholic cardinals locked in conclave Tuesday had no deadline for their decision to replace Benedict, who retired Feb. 28.
If the cardinals had succeeded in electing a pope -- an unlikely event on their first day in conclave -- the smoke would have been white. Burning the ballots alone produces white smoke. Burning the ballots with a chemical added -- it used to be damp straw -- produces black smoke, meaning no new pope yet.
Earlier, each cardinal put his hand on a Bible and swore an oath to vote fairly before taking a seat for meditation, CBS News reported.
Everyone except voting cardinals was expelled from the Sistine Chapel with the order "extra omnes," and only the electors remained, the report said.
The cardinals are under no deadline to select a pope, and will take four votes each day until successful.
At least 77 of the 115 cardinal electors must agree on a candidate to become the 266th pope.
French Cardinal Jean-Louis Tauran will announce the name of Benedict XVI's successor as pope to the world, the Vatican said.
Tauran, 69, has been chosen to declare "habemus papam," the formal Latin declaration meaning, "We have a new pope," once the conclave has elected a new leader of the Roman Catholic Church," the Italian news agency ANSA reported.
His announcement will come after white smoke curls up from the Sistine Chapel.
A career diplomat, Tauran is the first Frenchman to perform the role in more than 500 years.
Tauran is a native of Bordeaux and was ordained a priest in 1969.
The announcement of his selection came as a pre-conclave mass concluded at St. Peter's Basilica.
Cardinal Angelo Sodano invited the faithful to pray for the next pope.
"Let's pray so that the Lord grants us a pontiff who carries out his luminous mission with a generous heart," said Sodano, the dean of the College of Cardinals.
Earlier in the service, Sodano expressed the Church's thanks to Benedict.
The service was the last public event featuring the cardinals who will choose the new spiritual leader of the world's 1.2 billion Roman Catholics.
The technologically advanced Vatican still uses swirling smoke to announce whether a new pope has been elected, a spokesman said.
"For a church that has made much progress in the area of modern communications, computer technology, Internet and Twitter, the conclave still relies on smoke signals to let the world know of its results," the Rev. Thomas Rosica told The Washington Post.
Cardinals were assigned rooms randomly to discourage the forging of blocs in living quarters, The Wall Street Journal reported.
Vatican Television Center planned to broadcast the "fumate," or "smoke," live with a camera positioned about 10 yards away from the chapel chimney. The live video was to be available at player.rv.va.