The CBI today questioned the Corporate lobbyist Niira Radia for four hours at her New Delhi residence in connection with the 2G spectrum allocation scam. She along with former telecom minister A Raja were issued summons on Monday by the CBI to appear before it for questioning. Confirming the receipt of the summon, former Telecom Minister Mr. Raja in Chennai said, he is ready to cooperate with the agency in the investigation. The CBI also yesterday grilled former TRAI chief Pradip Baijal on the issue.Earlier, the Enforcement Directorate too had grilled Radia on allegations of money-laundering. The CBI earlier raided over 30 places in Delhi and Tamil Nadu on December 15 and questioned several persons informally. In the just concluded winter session of the Parliament, the CAG report on 2G spectrum scam was tabled. The report has pegged a huge revenue loss to the exchequer. Supreme Court is closely monitoring the multi agency probe in the allocation of 2G spectrum to certain telecom firms. The apex court has asked CBI and ED to submit status reports on their probe to it by February 10, when the 2G spectrum case will come up for hearing.