Concerned over the alleged scam involving hundreds of crores in the rerouting of international calls, CBI has launced a probe into the working of Reliance Infocomm and some other top private telecom operators.The probe by CBI comes amid a major crackdown by the department of telecom (DoT) and telecom PSUs, which have imposed stiff penalties that have been challenged by Reliance Infocomm.CBI, which has initiated the probe suo-motu, has asked the concerned authorities to furnish relevant details of international telecom traffic that is alleged to have been re-routed as local calls to avoid payment of levy to telecom PSUs, CBI officials said.The investigating agency stumbled upon the case during its investigations in the illegal telephone exchanges busted in Tamil Nadu, Kerala and Andhra Pradesh recently during the agency's special drive on February 2.CBI officials said that during its investigations into the functioning of illegal exchanges in the southern states, it had found involvement of certain private telecom companies and some officials of DoT. They said the companies had been asked to provide relevent details to the economic offences wing of the CBI.