Mary Elizabeth Whitehead, an American NGO (non-governmental) worker, was stopped from boarding a flight out of Cairo today, the Associated Press reported.
Security officials speaking on the condition of anonymity told AP that Whitehead was on a no-travel list compiled by Egypt's attorney general.
An American official who did not want to be named also told AP Whitehead was not thought to be among the 43 NGO workers Egyptian authorities charged with illegally using undisclosed foreign funding in a case that has severely strained Cairo's ties to Washington.
Over a dozen of the accused are US citizens -- Egyptian and American figures differ at 19 and 16, respectively -- with Germans, Palestinians and Jordanian citizens also among those charged.
Egypt's state-run Middle East News Agency said Whitehead was detained as she was boarding a Lufthansa Airlines flight to Frankfurt, Germany, according to Bloomberg.
The incident is being discussed between US and Egyptian officials, an official told AP.
More from Global Post: Egypt: Trial date for pro-democracy activists set
Bloomberg quoted a State Department officialas saying on Wednesday that US officials are considering cutting some of the $1.3 billion the US provides to Egypt in military aid over the high-profile case, which includes charges against the son of US Transportation Secretary Ray LaHood.
The trial, with charges carrying sentences of up to five years, is set to start on February 26.
Arizona Republican Senator John McCain and US officials met with top Egyptian authorities earlier this week in an effort to resolve the dispute.
The case targets several prominent US groups, such as the International Republican Institute, the National Democratic Institute, and thinktank Freedom House.
Local rights activists in Egypt, meanwhile, accuse the country's transitional rulers of using the case to blunt opposition activity there, said AP.