Top industrialist Ratan Tata and corporate lobbyist Niira Radia were today quizzed by Parliament's Public Accounts Committee (PAC) in connection with alleged irregularities in the 2G spectrum allocation. Tata appeared before the committee at three PM and faced questions on the subject. Earlier, PAC questioned corporate lobbyist Niira Radia over two hours in connection with the 2G scam. Radia's tapped phone conversations with politicians, corporates, bureaucrats, and journalists form a key part of investigations into the 2G spectrum scam. PAC chairman Murli Manohar Joshi today said the committee would probe all aspects of 2G scam. Speaking to reporters outside Parliament, he said the committee will look into the 2G scam in its totality. Last week, CBI has filed its first chargesheet in the case against Former Telecom Minister A Raja and eight others. Raja is in jail for alleged irregularities in the allocation of 2G spectrum licenses. A Joint Parliamentary Committee (JPC), chaired by Congress leader P C Chacko, has also been set up to look into all the details of the 2G spectrum allocation from 1998 to 2008.