The source at the embassy in Cairo said the victim, found hanged in a cell, was not James Henry, the name which had been given by Egyptian security officials.
Another name was provided by the source but it was not confirmed and there were no details about the victim.
Henry is a 55-year-old retired military officer who was arrested for breaking curfew, officials said.
A statement from prosecutors said he was arrested Aug. 28 en route to the Gaza Strip with "a map of Egypt and a modern electronic device [that is] currently being examined."
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