F1 Visa- administrative processing

[Hkaya 1]

Hi everyone I am from Turkey, I will start studying PhD at illinois institute of technology starting August 22. My visa appointment went very well, the officer asked me only three questions, didn't ask for any additional documents and instantly gave me an approval. He even wished me good luck. However, I got my passport back 10 days later, with a yellow-colored paper attached (and without a visa). It was explained that my application required further administrative processing, but it wasn't explained why. Is there anyone here who had a similar experience? Why could this have happened to me? My name and surname are very common in Turkey, also I will be studying computational drug design. Could these facts have raised suspicion about my application? How long did it take you to get your visa issued? Is there anything at all that can be done to expedite the process (although I know the answer is simply no, but one can always hope). If I can't get my visa in time, I will lose my TAship and will have to defer my admission. Thanks in advance.