The Securities and Exchange Board of India (Sebi) has initiated enforcement action in the National Stock Exchange (NSE) co-location case, chairman Ajay Tyagi said at a press conference on Thursday. The regulator said the enforcement action would be completed shortly since all investigation reports had been examined. The investigations, Tyagi said, have nothing to do with NSE\u2019s delayed initial public offering. The capital markets watchdog has been investigating alleged lapses in high-frequency trading offered through NSE\u2019s co-location facility. Sebi was investigating allegations that some brokers had unfair access to NSE\u2019s high-frequency trading systems. In March, the NSE management said its attempt at settling the case had not succeeded with the consent application being returned by Sebi. The exchange\u2019s Rs 10,000-crore IPO has been hanging fire because of the probe into allegations some brokers allegedly received preferential treatment in terms of faster access to information. These instances occurred while Chitra Ramakrishnan was the NSE managing director. \u201cWe had set up an investigating authority last year in May with a team of officers. We have got inputs from the forensic auditors and from the technical committee,\u201d Tyagi said. The Sebi chairman added all recommendations had been examined and that the regulator has taken a view on what is to be done. \u201cActions are being initiated against various entities, institutions, and individuals. I leave it at that,\u201d Tyagi said.