WASHINGTON (AP) — The New York Stock Exchange is paying $5 million to settle federal civil charges that it gave some customers an unfair head start by providing them with trading data ahead of the wider public.

It marked the first time the Securities and Exchange Commission ever imposed a fine on an exchange.

The NYSE and its parent NYSE Euronext also agreed in the settlement to hire an independent consultant to review their systems for delivering market data. They neither admitted nor denied the SEC's allegations.

The NYSE provides tailored data on stock quotes and trades directly to certain customers. The SEC said that from 2008 to mid-2010 the exchange violated a rule by distributing the data to those customers before putting it in its global information transmissions.

The SEC said the exchange failed to monitor the speed by which its computers deliver the customized data packages, compared with its global transmissions.

The SEC also censured the exchange. Censure brings the possibility that the NYSE could face a stiffer sanction if the alleged violation is repeated.

NYSE Euronext said the "technology issues" which caused the problems cited by the SEC have been resolved. Changes to the exchange's computer system were completed in 2010 and 2011, the company said in a statement.

Most of the differences in delivery times for the data were milliseconds, NYSE Euronext said.

The company noted that the SEC didn't accuse the exchange of intentional misconduct or causing harm to investors from the data delays.

The SEC said the difference in speeds between the customized data for some clients and the wider data transmission became magnified on May 6, 2010, when the Dow Jones industrial average plummeted nearly 600 points in five minutes.

By then, the exchange had fixed the software problems that had caused the differences in delivery times in about half of the affected computer servers, according to the SEC. But under the stress of the massive trading volume and stock orders, some servers weren't able to get the global data transmissions out as fast as the customized data packages.

"Improper early access to market data, even measured in milliseconds, can in today's markets be a real and substantial advantage" that puts individual and long-term investors behind, SEC Enforcement Director Robert Khuzami said in a statement. "That is why SEC rules mandate that exchanges give the public fair access to basic market data," he said.