US regulators investigating last year’s ‘flash crash’ and other market swings have sent subpoenas to firms that do high-frequency trading, the Wall Street Journal reports. In high-frequency trading, companies use computer algorithms to identify opportunities which can allow them to profit through rapid-fire trades often measured in milliseconds. Some market participants believe these trading practices may have contributed to the May 6, 2010 flash crash, which saw the Dow Jones Industrial Average plunge 700 points in minutes. According to the WSJ, a report last year by the Securities and Exchange Commission and the Commodity Futures Trading Commission on the flash crash said, amid other factors, these traders’ moves helped fuel the day’s rapid selloff. The WSJ says that at least some of the subpoenas have been sent since the start of the summer, though it isn’t known whether the subpoenas will result in any enforcement actions, since a subpoena doesn’t necessarily reflect a suspicion of wrongdoing. For more on how HFT traders are impacting the markets see FT Alphaville. Read more