Federal regulators will head back to Capitol Hill next week to discuss the causes of the nearly 10 percent drop in stocks on May 6.
Securities and Exchange Commission Chairman Mary Schapiro and Commodity Futures Trading Commission Chairman Gary Gensler will testify Thursday morning before the Senate Banking Subcommittee on Securities, Insurance and Investment.
Regulators haven't yet pinpointed why the market dropped nearly 1,000 points then made a quick recovery late last week, Gensler and Schapiro told a House panel earlier this week.
Although nothing has been ruled out, the two regulators said there wasn't any evidence of trader error, computer hackers or terrorism. There will likely be multiple reasons for the market's free fall, which occurred on a day when stock volatility was heightened because of fears surrounding the European debt crisis as riots broke out in Greece.
The SEC and CFTC have formed a joint advisory group to look at market regulations to determine what happened on May 6 and what, if any, changes are needed.