If your credentials were already verified by ECFMG (like if you did that for giving USMLEs) then ECFMG wont send a request to your medical college, and will simply electronically verify your credentials to MCC within 2 weeks. However, if your credentials ARE NOT verified by ECFMG at this moment, they will contact your medical school and your med school has to respond. This is usually a very slow process, and via regular mail, it can take upto 2-3 months. Sometimes, even you will need to contact your medical school correspondents to stay in touch or make sure they have not slowed things down.
Good luck mate!