"The potential for giant high-speed computers to generate false trades and create market chaos reared its head again today," said Delaware senator <name>Edward Kaufman</name>. "The battle of the algorithms — not understood by nor even remotely transparent to the Securities and Exchange Commission — simply must be carefully reviewed and placed within a meaningful regulatory framework soon." <name>Kaufman</name>, along with senator <name>Mark Warner</name> from Virginia, called on Congress to investigate the cause of the mass sell-offs.

Nasdaq, meanwhile, says that all trades of stocks at prices 60% higher or lower than the preceding price at or around 2.40 PM "or immediately prior" are to be cancelled; it noted that it coordinated its move with the other exchanges.

Chief investment officer at Fort Pitt Capital Group <name>Charlie Smith</name> said: "I think the machines just took over. There's not a lot of human interaction. We've known that automated trading can run away from you, and I think that's what we saw happen today."

In the past three days, the DJIA has lost 631 points, or 5.7%, mainly over concerns about Greece's ailing, debt-burdened economy. <name>Peter Boockvar</name> an equity strategist for Miller Tabak, commented: "The market is now realizing that Greece is going to go through a depression over the next couple of years. Europe is a major trading partner of ours, and this threatens the entire global growth story."