The CBI sent a notice to former Telecom Minister A Raja to appear before it for questioning in connection with alleged bunglings in allocation of spectrum to some telecom firms that resulted in loss of at least Rs 22,000 crore to the exchequer.

Similar notices have been sent to others including corporate lobbyist Niira Radia while her close associate and former Chairman of Telecom Regulatory Authority of India Pradip Baijal was being stioned by the CBI sleuths on Monday, official sources said.

Baijal, a former Disinvestment Secretary, belonged to the 1966 batch of IAS from Madhya Pradesh cadre.

Raja, who is in Chennai, was served notice at his official residence under section 160 of Criminal Procedure Code to appear before the agency for questioning.

It was not clear as to when Raja has been summoned by the CBI.

Under this section, the person is asked to join the investigation and share all information that he/she may have about a case.

The premises of Raja, Baijal and Radia were searched by the CBI earlier this month in connection with the case.