Muslim Brotherhood leader and politician Mohamed Ali Beshr was handed a 15-day extension of his detention on Wednesday, according to state-owned Al-Ahram.
The order was handed down pending an investigation into Beshr’s alleged collaboration with the United States and incitement to violence.
Beshr, former minister of local development, was arrested on the morning of 20 November.
Unlike many top Brotherhoods leaders, Beshr was not arrested in the immediate aftermath of the ouster of former president Mohamed Morsi in July 2013.
Commentators and the media have speculated that he could be involved in talks with the Egyptian authorities. There has been no official statement to confirm this.
Egypt’s cabinet declared the Muslim Brotherhood a terrorist organisation in December 2013, and the listing was then ratified by a court ruling months later.