The head of the IMF, Dominique Strass-Kahn, is being questioned by New York police over an alleged sex attack on a hotel maid, say reports.
Mr Strauss-Kahn, 62, was taken off a plane at JFK airport, minutes before it left for Paris.
Police said he was being questioned but has not been charged.
The married former French finance minister is also a leading Socialist party figure and is considered a possible presidential candidate.
He is due to attend a meeting of European Union finance ministers in Brussels on Monday to discuss the bailouts of Portugal and Greece.
Paul J Browne, a spokesman for the New York Police Department, said the allegations had been made by a 32-year-old woman who worked at a Manhattan hotel.
The IMF had no immediate comment on the incident.
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