I just recently did two phone interviews (one with the professor on the admission committee and the other with prospective PI) and was told that if I was offered admission, they would invite me for an on-site interview for sometime next week.
After the phone interview, I emailed the program coordinator at the department regarding when the admission decision will be made. She told me she would know by this morning (morning of the day I have written this post), yet I am still waiting to hear back from them.
Would it be okay to email them back to ask whether I was offered admission or not? Or should I just wait?