Mumbai, March 11 -- India's lightly regulated market for pre-IPO shares is back in focus after the Enforcement Directorate (ED) launched a probe into the alleged sale of unlisted National Stock Exchange shares, a case that is renewing calls for tighter oversight of the fast-growing segment.

Last week, ED conducted searches at eight locations in Mumbai and Chennai as part of a money laundering investigation linked to the sale of shares of NSE, which is set to hit the public markets soon. The action targeted entities, including Atum Capital Pvt. Ltd, Optimus Financial Solutions Pvt. Ltd, Babli Investment Pvt. Ltd and Supremus Angel, along with their directors.

The agency alleged that these entities duped investors by promising unlisted NS...