To clarify - I am not looking for answers supporting or refuting aryan migration into or out of India. I have seen answers to similar questions. Also not looking for modern genetic or environmental theories in support or against.
I'm merely asking for contemporary evidence in form of Vedic suktas and optionally Summary of justification for the author's saying so. Avestan evidence, though may not be contemporary is also welcome.
Marut Sukta RV 5.53 is speculated to be telling how an aryan tribe entered Indian subcontinent indirectly. The claim being one needs to be familiar with geography to write such a poem.