"In pagan times the oracles and predictions ascribed to the sibyls were carefully collected and jealously guarded in the temple of Jupiter Capitolinus, and were consulted only in times of grave crises. Because of the vogue enjoyed by these heathen oracles and because of the influence they had in shaping the religious views of the period, the Hellenistic Jews in Alexandria, during the second century B.C. composed verses in the same form, attributing them to the sibyls, and circulated them among the pagans as a means of diffusing Judaistic doctrines and teaching. This custom was continued down into Christian times, and was borrowed by some Christians [emphasis added] so that in the second or third century, a new class of oracles emanating from Christian sources came into being. Hence the Sibylline Oracles can be classed as Pagan, Jewish, or Christian." Source: "Sibylline Oracles," The Catholic Encyclopedia
Translation: Despite what the Catholic Church says, there are really only two classes of Sibylline oracles, the authentic pagan oracles and a collection of Jewish and Christian forgeries. Forgery was a common practice in the early Christian church. For more information, see "Forgery In Christianity: A Documented Record Of The Foundations Of The Christian Religion," by Joseph Wheless.