Mohamed Nabawi, a former spokesman for the Tamarod movement which led to the ousting of President Mohamed Morsi, was arrested on charges of possession of drugs.
Nabawi was referred to Nasr City, east of the capital, which ordered his detention for four days pending investigations. His detention was later renewed for an additional 15 days.
The Interior Ministry’s Department of Drug Control said it found 128 grams of cannabis in Nabawi’s possession. He denied any knowledge of the drugs.
Nabawi said: “I do not take drugs, and what happened is that I was in Nasr City to meet a friend, and during my return, I was stopped by detectives who, after searches, found the seized narcotics.”
The prosecution accused the former spokesman of Tamarod movement of drug abuse and trafficking. His detention will be reassessed on Saturday.
Tamarod is a grassroots protest movement that has been behind the protests against Morsi in 2013, a year after he took office.
The group, whose name means “revolt” in Arabic, claimed it collected more than 22 million signatures for a petition demanding Morsi step down and allow fresh presidential elections to be held.