"A large investor using an automated trading software to sell futures contracts sparked the brief-but-historic stock market "flash crash" on May 6, according to a report by federal regulators released Friday

...the lack of buyers and the rapid selling of E-Mini futures contracts began to affect the underlying stocks and the broader stock indexes.

...It was the largest one-day drop on record.

Waddell & Reed, an asset management and financial planning company based in Overland Park, Kan., has been widely reported as the investor behind the sell order.

...SEC chairman Mary Schapiro and CFTC chairman Gary Gensler said in a joint statement that the report "reaffirms the importance of a number of the actions we have taken since that day.""We now must consider what other investor-focused measures are needed to ensure that our markets are fair, efficient and resilient, now and for years to come," the statement said.

In June, the SEC approved new rules that will halt trading uniformly across all U.S. markets for stocks experiencing wild price swings.

The so-called circuit breakers require exchanges to stop trading in an individual stock for five minutes across U.S. stock markets if the stock experiences a 10% price swing in the preceding five-minute period.

Rep. Paul Kanjorski, D-Pa., who chairs a House subcommittee on capital markets, praised the report but said more needs to be done to rein in the use of algorithms used by high frequency traders."