Several US citizens barred from leaving Egypt, are sheltering at the US embassy in Cairo.
The State Department says 10 foreigners, including six US nationals, have been stopped from leaving Egypt. Among them is Sam LaHood, son of US Transport Secretary Ray LaHood.
They are being held in Egypt amid a criminal investigation of the organisations where they worked. The premises of 17 pro-democracy and rights groups were raided in late December.
The BBC reports the inquiry is seen as an attempt to silence critics of the army's crackdown on street unrest.