Authorities are checking deals involving more than three dozen companies.
The economy, which grew at 6.5 per cent in the year ended March 2012, is expected to grow 5.7 per cent to 5.9 per cent this fiscal year, the slowest since 2002/03.
Investors including units of Morgan Stanley and Citigroup have agreed to buy 28.3 million shares of Bharti Infratel at Rs 230 apiece.