Human rights lawyer and activist Mahienour El-Massry and three others were released, hours after their arrest on Wednesday, according to Free Mahienour Facebook page.
El-Massry was arrested along with lawyer Mohamed Ramadan and two others.
The four detainees were held in El-Raml police station in Alexandria, according to legal activist Nazly Hussein.
According to the Free Mahienour Facebook page, El-Massry and the others were arrested in the Stanley Bridge area under the allegation that they were protesting, while they were not involved in “any form of demonstration”.
The page further asks not to protest in front of the police station, “in accordance with the wishes of Mahienour and the lawyers”.
El-Massry had been released from prison by the end of September, after an Alexandria Court accepted her appeal against a six-month prison sentence.
She was initially sentenced to two years in prison and fined EGP 50,000 alongside eight others for violating the Protest Law, after being arrested while participating in a protest in solidarity with torture victim Khaled Said on 2 December 2013.
Wednesday marks the third anniversary of the Mohamed Mahmoud clashes in 2011 when dozens died and hundreds injured during clashes with security forces in downtown Cairo.