A team of prosecutors arrived Sunday to Tora Prison on the outskirts of Cairo to continue questioning detained Muslim Brotherhood Supreme Guide Mohamed Badie and leading group member Mohamed El-Beltagy.
Badie is on trial, along with several other Brotherhood leaders, including his deputy, Khairat El-Shater, for inciting the killing of protesters in clashes at the group's Cairo headquarters.
El-Beltagy faces the same charges.
Clashes at the Brotherhood's headquarters in June left eight dead.
El-Beltagy also faces accusations of inciting the killing of protesters during clashes between supporters and opponents of deposed president Mohamed Morsi in early July.
Investigations into El-Beltagy were delayed Saturday because he reportedly suffered from fatigue.
Badie, meanwhile, reportedly suffered a heart attack Saturday. A team of doctors were sent to examine him. He is currently in a stable condition, reported Al-Ahram Arabic website.