When the Archbishop of Naples picked up the vial containing the 1700-year-old dried blood of the city’s patron Saint Januarius to present it to Pope Francis Saturday, someone in the Naples cathedral shouted: “Miracle.” According to witnesses, the blood of the saint had become liquid again—at least in part.

The archbishop, Cardinal Crescenzio Sepe said, “That’s a sign that Saint Januarius loves Naples and Pope Francis: his blood is half liquefied.”

Francis kissed the relic and played down the “miracle” saying: “If it’s only half liquefied it means that the saint only half loves us. We all need to convert more, so that the saint will be fully pleased.” Minutes later, however, the blood had reportedly reverted to a fully liquid state.

If true, this is the first time that Saint Januarius’ blood has ever liquefied in the presence of a pope, though this phenomenon has occurred on a number of other occasions. Some claim that the event has been occurring “up to 18 times each year for the past 600 years.”

Saint Januarius—or San Gennaro, as he is called in Italian—was an early bishop of Naples beheaded sometime during the persecution of the emperor Diocletian, which ended in 305AD, according to Christian tradition.

The first recorded liquefaction of the saint’s blood was in 1389, when a priest carrying the flasks with the dried blood was processing around the cathedral when he became aware that the contents had begun to liquefy and bubble. Since then the occurrence has become common, normally on days associated with the saint. The Catholic Church has no official position on the so-called miracle, but allows for the veneration of the saint’s relic.

Skeptics of the miraculous nature of the phenomenon have put forward various theories to explain the liquefaction of the blood, such as that the application of heat from the priest’s hands produce the melting of the red substance, but none has gained a consensus of opinion.

When Pope John Paul II visited Naples in November 1990, he went to the cathedral to venerate the relic, but the blood remained in its dried state. The same thing happened with Pope Benedict XVI, who visited in October 2007.

After Saturday’s “miracle,” Pope Francis put aside the papers with his prepared address, and spoke off-the-cuff to the priests and nuns gathered in the cathedral, urging them to “center their lives on Jesus,” and not be attached to worldly things, such as money.

“The devil,” Francis said, “always tempts us to jealousy, envy, infighting and hostility. These things destroy brotherhood and cause us to give a testimony of division,” he said.

Follow Thomas D. Williams on Twitter @tdwilliamsrome