Egyptian prosecutors extended the detention of an Al-Jazeera journalist accused of incitement and fabricating news for another 15 days on Wednesday, officials said.
Mahmoud Hussein, 51, an Egyptian national, flew to Cairo two weeks ago for a family holiday but was stopped and interrogated at the airport for several hours before being released.
Police raided his Cairo home on December 23 and arrested him. After being questioned again, he was ordered to be detained.
It was the latest move against the Qatar-based broadcaster which Egypt accuses of supporting the outlawed Muslim Brotherhood of ousted president Mohamed Morsi.
The interior ministry said after Hussein's arrest that he was implicated in an Al-Jazeera "plot" aimed at "fomenting discord and inciting against state institutions... and broadcasting false news as well as fabricated news reports and documentaries."
In November, Al-Jazeera broadcast a documentary called "The Soldiers" in which former conscripts spoke about compulsory military service in Egypt, drawing criticism from the media.
Al-Jazeera Managing Director Yasser Abu Hilalah denounced Hussein's arrest, saying the broadcaster "will continue to cover Egypt and we don't succumb to pressure."
Egypt provoked international condemnation in 2013 when it arrested three Al-Jazeera journalists, including a Canadian and an Australian, and sentenced them to jail on similar accusations.
They were later released.
Their arrest, months after the military overthrew Morsi who had been backed by Qatar, coincided with a massive crackdown on his supporters and the Muslim Brotherhood being blacklisted.