The Central Bureau of Investigation appears to have got hold of evidence to prove how Satyam [Get Quote] Computer's revenues were inflated. It has sent its officials to Mumbai to probe the role of the regulators in the case pertaining to the Rs 7,800 crore (Rs 7.8 billion) accounting fraud in the IT firm.

Official sources said a CBI team was in Mumbai to understand the share transactions of the Satyam group of companies on the National Stock Exchange and the Bombay Stock Exchange.

They said the modus operandi used by the accused involved generating fake invoices, showing imaginary money being pumped into the financial system and profits which were never there.

The CBI, at present, is questioning disgraced former Satyam chairman B Ramalinga Raju and four others, including the suspended auditors of Price Waterhouse. Their custody was handed over to CBI recently.

Besides Ramalinga Raju, his brother Rama Raju, Satyam's former CFO Srinivas Vadlamani, G Gopalakrishnan and Srinivas Talluri have been arrested in the case.

The agency is probing the rotation of funds and the role of front companies used in the rotation of funds, sources said. They added that the conduct of the regulators was also being probed and, if need be, some officials may also be probed.

Experts, including CAs from the Institute of Chartered Accountants of India and the Institute of Cost and Works Accountants of India are assisting the CBI in probing the role of regulators in this case, sources said.

They said that inflated revenues have been unearthed and relevant documents taken over.

The CBI registered a case against Ramalinga Raju and others for their involvement in what it called a unique accounting fraud at the IT company.

The scam, 'unique' in its own kind, has made the CBI constitute a multi-disciplinary investigation team headed by Deputy Inspector General VV Lakshmi Narayana. The team will be headquartered in Hyderabad to undertake a thorough probe.

The case against the accused was registered under 120-B (criminal conspiracy), 409 (criminal breach of trust), 420 (cheating), 467 and 468 (forgery), 471 (using forged document as genuine), 477-A (falsification of accounts).

The case was handed over to the CBI on February 18 by the centre after a request for the same was received from the Andhra Pradesh government.

On January 7, Ramalinga Raju confessed to the Rs 7,800 crore (Rs 7.8 billion) fraud and accepted that he had cooked the company's account books and inflated profits over the past several years. Three days later, he was arrested by the Andhra Pradesh police.