The comprehensive "flash crash" report that U.S. regulators issued this month will not alone restore investors' confidence in markets, though it is a good start, the deputy chief executive of NYSE Euronext said on Monday.

"It shines a good light on what happened in the origin of the incident, and it brings the attention on both sides of the ocean on the side effects of market fragmentation," Dominique Cerutti told Reuters on the sidelines of the World Federation of Exchanges conference in Paris.

The much anticipated report jointly issued by the Securities and Exchange Commission and the Commodity Futures Trading Commission October 1 detailed the fast-paced, complicated breakdown in U.S. stock and futures markets on May 6, in which the Dow Jones industrial average dropped some 700 points in minutes before sharply rebounding.

A single, large, computer-executed sell order helped trigger the unprecedented crash, which was quickly exacerbated by high-frequency traders scrambling to hedge positions and ultimately by a disappearance of liquidity, the report concluded.

Since the crash, funds have left mutual funds and overall trading volumes have declined, stoking speculation that investors have lost a measure of confidence in the mostly electronic U.S. stock market, in which trading is done on 50 some venues.

"The flash crash is linked to fragmentation of the market," said Cerutti, who heads up the technology division at exchange operator NYSE Euronext, parent of the Big Board and exchanges throughout Europe.

"It's a real life, sad example that bad things can happen if you don't take care. We should not wait for that kind of accident to try to understand how we can make the market better."