Mohamed Morsi's spokesperson Yasser Ali held in Egypt
Ali, who has also been a Muslim Brotherhood leader, "referred to Dokki police station in Giza", Xinhua reported citing the minister.
Since Morsi's removal by the military in early July, hundreds of Brotherhood members, including top leader Mohamed Badie, and thousands of their affiliates have been arrested over various charges.
The government on Wednesday declared the Brotherhood as "a terrorist organisation" after a blast on Tuesday rocked a security department headquarters in Daqahliya province north of the capital Cairo, killing 16 and injuring over 100.
A Sinai-based jihadist group called Ansar Beit al-Maqdis, which is Al Qaeda inspired and does not have direct connection with the Brotherhood, claimed responsibility for the blast.