Cardinals have failed to reach the required two-thirds majority in their first vote to choose a new pope in the Vatican.
Black smoke emerged from the Sistine Chapel chimney at 8pm, indicating they had been unable to agree.
Crowds in St Peter’s Square had been kept waiting longer than expected and most were hoping for the white smoke that signals the arrival of a new pontiff.
There was only one vote today, but from Thursday the 133 cardinals will hold two votes in the morning and two in the afternoon until at least 89 pick the same name.
The conclave started on Wednesday afternoon after cardinals swore an oath of secrecy and the doors of the Sistine Chapel were shut to the outside world.
They have given up their phones and are cut off from the outside world until a new pope is chosen.
The most recent conclaves – for Pope Francis in 2013, Pope Benedict XVI in 2005 and Pope John Paul II in 1978 – all lasted less than three days.
The voting takes places beneath Michelangelo’s legendary frescoes and the chapel – normally a packed tourist site – has installed tight security.
It’s been swept for listening devices, signal jammers have been installed, and its windows have been covered to protect from spy drones.
Lead seals have also been put on 80 doors at the conclave site to stop people going in and out.
The cardinals will sleep and eat at the Casa Santa Marta, a guest house within the Vatican where Pope Francis lived, until the process is over.
They cardinals began Wednesday by taking mass, before a solemn two-by-two procession into the Sistine Chapel in the afternoon.
Dresses in their red garb, they chanted the Litany of the Saints and Veni Creator – a hymn imploring the saints to help them find a new leader.
They then each came forward to take an oath of secrecy, placing a hand on the gospel and also promising not to allow any outside influence.
The final piece of theatre was the Latin declaration “Extra omnes” (“everyone else out”) and Archbishop Diego Ravelli, an aide to the late pope, pushed the the doors shut.
Conclave is beginning 16 days after Pope Francis’s death, which came after a long hospital stay with pneumonia.
Many experts believe it will come down to a choice between someone who will continue his progressive approach and a more conservative candidate.
Among the favourites is Luis Tagle, a cardinal who could become the first Asian pontiff, and who’s been likened to Pope Francis.
Two Italians are also seen as strong contenders: The Archbishop of Bologna, Matteo Zuppi, and the so-called “deputy pope” Pietro Parolin.
The pope’s identity is normally revealed soon after the white smoke emerges, when he steps onto the balcony to wave to the crowds in St Peter’s Square.
