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Nasser Nasser, Associated Press
An Egyptian youth walks past graffiti that includes a defaced picture of military ruler Field Marshal Hussein Tantawi and Arabic that reads, "Mubarak's dog, no for the military rule, freedom," in Cairo, Egypt Thursday, Feb. 9, 2012. Egypt is refusing to back down in a dispute with the U.S. over Cairo's crackdown on nonprofit groups despite Washington's threats to cut aid, while the military deployed troops to the nation's streets after a surge in violence and protests against its rule.

CAIRO — A British woman has been barred from leaving Egypt because she is on a list of foreigners under investigation over ties to foreign nonprofit groups accused of fomenting unrest in the country.

An airport security official says she was ordered off a London-bound plane Friday in Cairo.

The official says the woman works at a U.S. nonprofit group accused of illegally using foreign funds to finance activities to destabilize Egypt. Sixteen Americans and 27 Europeans and Egyptians have been referred to trial on those charges. At least 10, including six Americans, have been barred from leaving.

The case has threatened Egypt-US relations, and shocked pro-democracy groups.

The official spoke on condition of anonymity to discuss the case. There was no immediate comment from the British Embassy.