H1b petition sent back to USCIS

Question

Hi,

I have appeared for H1B visa interview on May 18th, 2012 at mumbai consulate and was issued 221g(Green) for additional document submission(EVC model). Last week I came to know that petition has been sent back to USCIS for further review. My extension is valid till Sep 2013.

In worst case scenario if USCIS sends NOIR to my employer, can I change employer after NOIR notice and before USCIS's final decision or employer change process needs to be started even before USCIS sends NOIR to my employer? Basically I am not thinking to change my current employer at this point but also wants to make sure that what options I will have if things goes wrong.