General Electric shares fell sharply for a brief period in New York as investors reacted to what turned out to be a hoax press release.
The Associated Press reported a statement apparently from the company saying it planned to repay a $3.2bn tax refund received from the US government.
Minutes later General Electric said the release was a fake. The hoax was the work of activists wanting to draw attention to General Electric's use of tax avoidance measures.
A tiny guerrilla team calling itself Yes Men claimed responsibility for the stunt, their latest in a series aimed at companies which take advantage of generous tax loopholes.
GE shares trading on the New York Stock Exchange closed down 0.35% at $19.94.
Two global vehicles
'Further plug advice gap'
Must appoint separate CEOs and boards
Advisers do come out well
Will report to Mark Till