Amazon post background verification process

If there are any Amazon recruiters here. I recieved an offer from Amazon which I recently accepted. My background verification is also complete. The next steps my recruiter says is my documents have been sent to immigration. I am currently on Student Visa. I also recieved the third party relocation confirmation email. But the recruiter advised me not to Resign yet just to be sure. I have not yet recieved the official New Hire material or the final offer letter to be signed. I was wondering if I have to be worried about anything?