The five political activists were to be charged with using social media to incite violence, The New York Times reported Monday.
As many as 1,000 anti-Islamist activists attacked the headquarters of the Muslim Brotherhood Friday night. About as many Brotherhood supporters surrounded the building to protect it. Police used tear gas to separate the sides, but before the conflict ended several Brotherhood buses were burned and about 100 people were injured.
President Mohamed Morsi, who heads the Freedom and Justice Party, but has close ties with the Brotherhood, blamed the attack on political opponents. In a Twitter message Sunday, he charged opposition leaders with "providing a political cover for violence."
The public prosecutor, who was handpicked by Morsi, said in a statement Monday the five defendants had used Facebook and Twitter to incite people to "burn down the headquarters of the Muslim Brotherhood and to murder some of its members."
A search of the activists' social media accounts by the Times found no such incendiary statements prior to the Friday night incident. One defendant, Alaa Abdel Fattah, had argued against violence.