A dramatic fall in the Dow Jones industrial average appears to have been caused by a trader hitting the button for 'billion' not 'million'.
The Dow Jones fell by nearly 1,000 points, and the Nasdaq and New York Stock Exchange announced that all trades more than 60 per cent above or below market that occurred between 2.40pm and 3.00pm New York time would be cancelled.
A report on CNBC said that the problem came when a deal involving Proctor & Gamble shares was incorrectly entered.
"We, along with the rest of the financial industry, are investigating to find the source of today's market volatility," Citigroup said in a statement. "At this point we have no evidence that Citi was involved in any erroneous transaction."
Proctor & Gamble shares fell by over a third on the day's trading.
"We don't know what caused it," said Procter & Gamble spokeswoman Jennifer Chelune. "We know that that was an electronic trade, and we're looking into it with Nasdaq and the other major electronic exchanges."
Systrom and Krieger taking time off "to explore our curiosity and creativity"
Comcast's £29.7bn winning bid more than twice the £13.7bn Rupert Murdoch valued Sky at just eight years ago
A nuclear strike has been considered, but Bruce Willis is nowhere in sight
Spray-on antenna could enable seamless integration of antennas with everyday objects