All work for the Middle Eastern news agency Al Jazeera and are accused of making up news stories and disturbing public peace, instilling terror, harming the general interests of the country, possessing broadcast equipment without permit and disseminating images contrary to the truth.
The names of the journalists have not been revealed but they are thought to include UK citizens Mohamed Fahmy and Peter Greste, formerly a BBC man.
Bombs in Cairo, including two on Friday which wounded six policemen, have been blamed on the Brotherhood which was declared an illegal terrorist organisation at the end of last year.
Founded in 1928, the party is Egypt's oldest and largest Islamist organisation with a political ideology based on the Koran. It became the main opposition to Egypt's reviled president Hosni Mubarak, whose fall from power in 2011 paved the way for the election of president Mohammed Morsi, Egypt's first civilian and Islamist leader.
The Brotherhood was fatally weakened last July when Morsi was ousted after a year in office. He now faces trial on charges including treason, murder and carrying out acts that undermined Egypt's stability and security,
One of the reasons for the arrest of the journalists is that Al Jazeera is based in Qatar, a major Brotherhood supporter. Many Egyptians believe this link has been responsible for much of the violence in the months since Morsi was deposed. They cite the Muslim Brotherhood's espousal of sharia law and the persecution of Christians as evidence of extremism policy to make Egypt embrace Islamic rule.
With Morsi's trial due to reopen soon there have been Government briefings that the Brotherhood has links to al-Qaeda, fostered with Qatar's help. Officials point to the revelation of alleged phone calls between between Morsi and Muhammad al-Zawahiri, Egypt-based brother of al-Qaeda leader Ayman al-Zawahiri. The authenticity of these recordings has been disputed but with rumours sweeping Cairo it has not been hard for the regime to paint the Brotherhood as jihadists linked to terrorism.
The Brotherhood's fall from political power has been spectacular: most of its leaders are incarcerated, Morsi is on trial for his life and many of his supporters have been silenced or killed.