The Securities and Exchange Commission on Wednesday postponed a decision on whether to approve the heavily scrutinized sale of the Chicago Stock Exchange to a group led by Chinese investors, despite a recommendation from its staff to certify the deal. The move further delays an effort to revitalize the 135-year-old market by transforming it into a US listings outpost for Chinese companies, The Wall Street Journal reports. The three-member commission will vote on the exchange’s application instead of allowing SEC staff to decide the matter. The $20 million deal has weathered scrutiny from a bipartisan group of US lawmakers skeptical of a string of Chinese bids for American firms. The lawmakers questioned whether Chinese owners could sift secrets about trading strategies and other matters from the stream of orders that rush through exchange systems. The Committee on Foreign Investment in the US shared some of those concerns, people familiar with the matter said.