The entities under watch include individuals whose names figure in a list of over 700 Swiss bank account holders, as also the bankers and associates related to certain banks whose Switzerland-based branches are under scanner.
Besides, 10-15 listed Indian companies including a few blue-chip names directly or indirectly linked to these banks and their Indian customers are also under a close tab for any suspected market manipulations, senior officials said.
It is suspected that some of these entities may have brought back their illicit wealth through the stock market route, by using complex fund structures of certain overseas funds, including those floated by select European banking giants.
The official said that a few large global banks are under scanner, although it is also possible that the banks themselves might be unaware of the illicit activities being carried out by their executives for the benefit of their clients.
He further said that these bankers are suspected to have first convinced their clients to move their funds to non-Swiss locations like Singapore, Dubai and London before eventual transmission to India, to avoid the ever-growing glare or regulatory and intelligence agencies on funds and entities linked to Switzerland.
While jurisdictions like Mauritius and Cyprus earlier used to be preferred as such intermediary locations, these places have themselves come under scanner of Indian agencies and therefore bankers are opting for some new routes.
Refusing to disclose the name of these individuals, banks or the listed companies under scanner, a senior official said these include some really big names and those figuring in the lists of richest persons and biggest companies, but that disclosure of further details at this moment may jeopardise the probes that are still in the initial stages.
These probes come at a time when India has strongly objected to Switzerland's denial of information about account details of certain Indians at HSBC's Swiss bank branches, in whose cases "incriminating evidence of tax evasion" have been found here.
In his third letter to Switzerland in this regard, Finance Minister P Chidambaram said that the interpretation made by Switzerland that it cannot share information as per India's request was not in accordance with international standards.
Switzerland has long been perceived as a major safe haven for alleged black money stashed by Indians and other foreign nationals due to its strong banking secrecy laws.
The issue has gained further significance in the recent past due to the ongoing elections where the matter of black money allegedly stashed by Indians abroad has also become a major poll issue.
Under global pressure, Switzerland has agreed to ease its banking secrecy laws in recent years and also signed a revised tax treaty with India in 2011 to facilitate greater flow of information about alleged black money.
However, it has refused to share information with India about the accounts mentioned in the so-called 'HSBC list' which India had received from France through a bilateral treaty.
France had received that list after data was stolen by a disgruntled HSBC employee in 2011 and those names eventually found their way to tax authorities across the world including India.
The Finance Minister further said Switzerland was putting unusual pre-conditions for sharing information which appear to be "intended to refuse assistance" and such refusal amounts to Swiss authorities providing protection to the people "found to have evaded Indian taxes".
Switzerland has rejected India's request on the pretext that the information was being sought on the basis of stolen data and it claims that its local laws do not permit exchange of information in such cases where some criminality may be involved for getting the data.
While Indians are said to be no more that much comfortable with Swiss banks now, Mauritius has also lost its place as a preferred gateway for investments coming to India.
Once known as the biggest gateway for flow of funds into India, Mauritius has slipped to the second place after the US in terms of quantum of money being brought in by overseas investors into Indian markets.
According to the government data, the foreign direct investment inflows from Mauritius have also fallen sharply on fears of possible re-negotiation of the tax avoidance treaty between the two countries.