(Bloomberg News) NYSE Euronext will pay $5 million to resolve U.S. regulatory claims that the New York Stock Exchange violated rules by giving certain customers a head start on trading information.

The exchange sent data through two proprietary feeds to paying customers before relaying the information to the so- called consolidated feed, which distributes trade and quote data to the public, the Securities and Exchange Commission said in an administrative order filed today. Investigators are conducting similar reviews of other exchanges, according to two people with knowledge of the probes, which aren't public.

The SEC penalty, the first of its kind against an exchange, comes as lawmakers and regulators question whether retail investors are being harmed in an increasingly fragmented marketplace of high-speed, computer-driven trading. NYSE's practice was discovered in the SEC's investigation of the so- called flash crash of May 2010, in which $862 billion was erased from equities in 20 minutes.

"The NYSE chose ground-shipping for sending market data to the consolidated feed but used next-day air for its paying customers," Sanjay Wadhwa, deputy chief of the SEC's market abuse unit, said in an interview.

The practice violated Regulation NMS, which obliges exchanges to give the public fair access to market information, the SEC said. The NYSE violated SEC rules "over an extended period of time" starting in 2008 by failing to monitor the speed of its proprietary feeds compared to the consolidated feed, the agency said in its order.

While the SEC has previously faulted exchanges for misconduct by employees, today's action marks the first time the agency has fined an exchange for having faulty systems in place that systematically violated securities rules.

"The timing differentials stemmed from technology issues, not from intentional wrongdoing by the exchange or any of its personnel," NYSE Euronext Chief Executive Officer Duncan Niederauer, said in a statement. The company, which operates exchanges in the U.S. and Europe, will "ensure that our market operates with the utmost fairness and transparency," he said.

NYSE Euronext completed systems modifications in 2010 and 2011 that eliminated the technology issues that were the subject of the investigation, according to the statement. The company also agreed to hire an independent consultant to assess its compliance systems.

"As investors and traders we need to understand that information is being distributed fairly and equally to the market," Larry Tabb, chief executive officer of research firm Tabb Group LLC in New York, said in an interview. "We can't have a market where structural inequalities present the optics that one class of investors has an advantage over another."