Like I said, we don't know yet. They will eventually be explained via simple physical explanations - as every other one has been.
Remember the Tunguska Blast? That was claimed to be aliens for a long time. Turns out it was just a meteor. The fact that they couldn't explain it for decades did not mean it was aliens.
Ever hear about the six alien spacecraft found in England in 1967? The government investigated; even took one to the
Atomic Weapons Establishment at
Aldermaston to be studied. They were a college hoax.
Etc etc.
Imagine you were a pathologist and regularly did autopsies. You do thousands over the years. Then a new cadaver comes in for an autopsy. What's more likely? That you will do that autopsy and find the usual viscera, along with perhaps a pathology - or that it is full of extraterrestrial creatures masquerading in a human suit?