Corporate lobbyist Niira Radia is likely to be questioned today by the CBI in connection with the 2G spectrum scam. She was served the CBI summons yesterday asking her to come to the CBI headquarters immediately. The CBI had said in an affidavit to the Supreme Court last month that Radia's role would be examined. It had told the court that the case had irregularities of "enormous magnitude" having international ramifications.