Prosecutors have filed a new incitement charge against Muslim Brotherhood Supreme Guide Mohamed Badie.
Badie was charged on Wednesday with inciting the storming of a police station in Cairo's Sixth of October City following the deadly dispersal of pro-Morsi sit-ins in Cairo on 14 August.
Islamist-leaning former MP Mohamed El-Omda, already detained on other incitement charges, faces the same allegations as Badie.
Badie's detention was extended for a further 15 days.
The Islamist leader is already on trial, alongside his two deputies Khairat El-Shater and Rashad Bayoumi, for inciting the killing of protesters at the Brotherhood headquarters on 30 June.
In addition, Badie is being investigated for attempted murder, incitement of murder and incitement of chaos during the pro-Morsi sit-in at Rabaa Al-Adawiya, and clashes in Bein El-Sarayat, at the Republican Guards headquarters and outside the presidential palace.
Egypt's interim authorities launched a crackdown on the country's largest and oldest Islamist group following Morsi's ouster. Hundreds of Brotherhood members, including most of the group's higher echelons, are facing prosecution.