'Sources tell CNBC the erroneous trade may have been made at Citigroup .....
... According to a person familiar with the probe, one focus is on futures contracts tied to the Standard & Poors 500 stock index, known as E-mini S&P 500 futures, and in particular a two-minute window in which 16 billion of the futures were sold.'
and
Both markets (NASDAQ and NYSE) said they will cancel all trades more than 60 percent above or below market that occurred between 2:40 p.m. and 3:00 p.m. New York time.
