Central Bureau of Investigation officials checked the Airtel office in Gurgaon and Vodafone office in Mumbai and Delhi, and the residences of former telecom secretary Shyamal Ghosh and former deputy director general in the telecom ministry J.R. Gupta Saturday morning.

On Friday, the CBI registered a case in the allocation of additional spectrum to the private telecom firms when the late Pramod Mahajan was telecommunications minister in the National Democratic Alliance (NDA) government.

"Bharti Airtel has always maintained the highest standards of corporate governance and regulatory compliance. We would like to categorically state that all the spectrum allotted to us from time to time has been strictly as per the stated government policy," said a spokesperson, Bharti Airtel.

Vodafone said in a statement: "All our documents are in complete compliance with the governing laws and regulations. Vodafone India is completely co-operating with the officials and will provide them all required details as part of their checks."