Speeding up its probe in the multi-crore 2G Spectrum scam, the Central Bureau of Investigation (CBI) today questioned Sanjay Chandra, Unitech Managing Director even as the agency has summoned officials of several other companies in connection with the case.''The CBI questioned Unitech MD Sanjay Chandra in relation with the 2G Spectrum scam,'' a CBI official said.Unitech, which was allotted 2G licences for 22 circles for Rs 1658 crore, sold 60 per cent of its shares to Telenor of Norway for Rs 6,100 crore even before the rollout, causing a loss to the exchequer.The sources said one of the co-promoters of DB Realty was also grilled.When asked about the companies summoned, the CBI official said, ''We have called several officials of various companies for questioning. This is a part of the investigation.'' Widening the probe into irregularities in the 2G spectrum licence allocation, the agency has also summoned former Telecom Minister and BJP leader Arun Shourie to appear before it. Shourie will be questioned on February 21.The CBI has also been grilling several officials of Anil Ambani-led ADAG group in the scam, which according to the Comptroller and Auditor General of India (CAG) report, caused a loss of Rs 1.76 lakh crore to the exchequer.The agency had summoned a senior ADAG official for questioning at its headquarters here.The Supreme Court has directed the CBI to go after all illegal beneficiaries of the irregularities in the licence allocation, from a normal official to a billionaire.Both the DB Realty and Reliance Telecom were equity holders in Swan Telecom, one of the major beneficiaries of the scam.The agency is continuously grilling former Telecom Minister Andimuthu Raja and Shahid Balwa, promoter of DB Realty.A CBI Special court yesterday sent Raja and Balwa to four-day CBI remand. The court ordered remand for Raja till February 17 and Balwa till February 18. Balwa's company allegedly got favours in the spectrum allocation and caused the national exchequer a loss of over Rs 22,000 crore.