MICHIGAN STATE TAX RETURN STILL PENDING

I E-Filed my taxes on February 13th. I received my Federal return within a few weeks but still waiting on my Michigan State return. I filed forms MI-1040 and MI-1040CR. I contacted them and they stated my return was randomly selected for a manual review. Any ideas what is holding it up and how long it will take to receive my return? I haven't received any correspondence via email or postal mail from them.