The Central Bureau of Investigation (CBI) has registered a preliminary inquiry against unknown officials of Adani Group, owned by Gautam Adani, and is probing an alleged over-invoicing fraud of Rs 2,300 crore.

The CBI registered the inquiry last month in the wake of allegations that the Group availed various credit facilities from public sector banks for procuring power generation and transmission equipment from vendors in China and South Korea through a UAE-based intermediary by overvaluing the original price.

"The documents were routed through Electrogen Infra, the UAE intermediary. While actual worth of the equipment was remitted to the supplier, the inflated extra amount was siphoned off," said a senior CBI official.

According to the CBI, the Adani Group has availed credit facilities from State Bank of India, Punjab National Bank, Vijaya Bank, Oriental Bank of Commerce, Canara Bank and State Bank of Maharashtra.

"We are probing the matter as public sector banks are involved. The DRI (Dept of Revenue Intelligence) has assessed the total over-valuation for 2011-13 to be around Rs 2,300 crore," said a senior CBI official. The DRI complaint is the basis of the CBI inquiry.

Adani Group had allegedly availed huge loan facilities from public sector banks by showing inflated invoices. The CBI is also probing the involvement of bank officials.

Earlier this year, the DRI had issued a show-cause notice to Adani group companies alleging that the total declared value of goods imported under power and infrastructure heads was inflated.

Apart from the role of bank officials in the alleged fraud, which is under the scanner, the CBI is looking into allegations by DRI in its notice.

The agency may soon start questioning company officials and banks involved to probe if there was a criminal conspiracy and loss to the exchequer. The CBI is also likely to seek documents of the financial transactions between the banks and the companies.

The three group companies are Adani Power Maharashtra, Adani Power Rajasthan and Maharashtra Eastern Grid Power Transmission.

The CBI move follows a recent approval for an Adani group company by the government. The environmental clearances legalised its 8,481-hectare special economic zone (SEZ) in Mundra.

The SEZ had been in limbo since January when the Gujarat High Court declared it illegal and ordered the companies that had set up factories there to stop work.

The grant of environmental and coastal regulator zone (CRZ) clearances has resolved all pending issues till now, and it will lead to the construction of a desalination plant and an effluent treatment plant in the SEZ. Companies that had been restricted by the High Court from operating inside the SEZ are now expected to return.

Also Read: Adani group in trouble? CBI registers preliminary enquiry for over valuation and custom evasion