Okay, I might be open to the theoretical possibility, but what kinds of evidence could there be that miracles are actually possible?
But if the claim is that a strange event still happened at such and such place and such and such time, in other words, at a point in history, then there needs to be good historical evidence that holds up to scrutiny by the methods of historians, which cannot be simply repeated in a test-tube in a lab. That's called historiography. And that's what need to do with any event, including a report of an event that seems strange or inexplicable, such as a miracle.
Perhaps the best example of a miraculous event with well-attested historical evidence is the resurrection of Jesus. So to answer your question – the kind of evidence that we need to look into for a miraculous event is historical evidence.