VATICAN CITY (AP) — Black smoke poured from the Sistine Chapel chimney on Tuesday, signaling that cardinals had failed on their first vote of the papal conclave to choose a new leader for the world's 1.2 billion Catholics and their troubled church.

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.

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.