Dow Jones Newswires | The plunge in U.S. markets Thursday afternoon may have been caused by a
trader who accidentally placed an order that confused billion with
million in a sale of e-minis, the futures contracts tied to equity
indexes, according to speculation swirling on Wall Street’s trading
desks.

News coverage of riots in Greece had already pushed down markets. But an
electronic trading algorithm was said to have issued a massive sell
order on futures contracts tied to the S&P 500, according to a
long-time electronic trader of the products. The market may have dropped
on a mistaken order to sell $16 billion of e-mini S&P futures, as
opposed to $16 million, according to several people.

E-minis are traded at the Chicago Mercantile Exchange. Allan Schoenberg, a spokesman for CME Group Inc., said the exchange was examining trades but that the markets had functioned properly.

“Whenever the market moves up or down like the swings we saw today, we take a look to make sure everything’s operating properly. That’s exactly what we’re doing now,” Schoenberg said. “If the exchange finds anything amiss, it would report its finding on its website.”

The spokesman said there was no evidence of an error in the operation of the CME.