In the play Antigone, What happens to the the offering Tiresias places on the altar? Why?

In the play Antigone Teiresias gave an offering to the gods so he could understand the prophecy, but instead of receiving an answer he realized that some slime began to ooze out of the altar. As a result he did not received any answers. In fact, this happened because what Teiresias learn came from his guide, a young boy.