That is, by definition, the nature of science: natural explanations for natural processes.
As soon as you say, "God did it", then you are no longer scientific.
Of course, that doesn't mean you're wrong, it only means that science itself can't go there.
And if you'll give it a little thought, you'll realize that's just the way it should be.
After all, whoever would want some scientist defining what is, or is not, God?
And if you'll give it a little thought, the phrase "natural processes" also is a veiled attempt to EXCLUDE a creative God from the equation.
BTW: "Mother Nature" doesn't really exist either, however it conveniently sidesteps confronting the idea of a creating and sovereign GOD!