Egyptian prosecutors ordered the detention of two journalists, Amr Badr and Mahmoud al-Saqqa, for 15 days pending further investigations, the website Al-Ahram Online reported Monday.
The two journalists, arrested during the Interior Ministry's storming of the press syndicate on Sunday, were accused, among other things, of "spreading false news, inciting the public, and plotting to overthrow the regime," Al-Ahram reported, citing a judicial source.
The report added that "the prosecution is also questioning the two journalists on accusations of obstructing government administration, harming national unity and social peace."
Earlier Monday, the Egyptian Journalists' Syndicate called for the interior minister to be sacked after police raided the group's headquarters to arrest two journalists.
The syndicate described the Sunday night raid on its headquarters as "a blatant attack on the dignity of journalists," saying it was the first such incident since it was founded 75 years ago.
The move comes amid increased tension between authorities and the syndicate, which accused police of standing by while pro-government demonstrators attempted to storm its headquarters 10 days earlier.
Local media outlets reported that police blocked all the streets leading to the syndicate building in downtown Cairo as several journalists gathered outside to protest the arrest of their colleagues.
Journalists Amr Badr and Mahmoud al-Saqqa of the independent Yanair news site had started a sit-in in the syndicate building in protest of their arrest warrants, the state-run Ahram newspaper reported online.
The Interior Ministry denied that its forces had "stormed" the syndicate building and said that Badr and al-Saqqa had given themselves up peacefully when eight officers entered and informed them of the arrest warrants.
The ministry said it acted in consultation with prosecution authorities after learning that the two were "taking refuge" inside the building and accused them of "attempting to press the syndicate into a confrontation with security agencies and exploiting that to create a crisis."
The raid was highly symbolic, as the syndicate headquarters in central Cairo was the only place where protest was grudgingly tolerated under former dictator Hosny Mubarak, who was ousted in Egypt's 2011 uprising.
Citing a statement from the public prosecutor's office, Ahram reported on Monday that nine suspects, including the two journalists, have been accused of publishing false news and rumours on Facebook ahead of April 25 to incite the public into clashing with police and military forces, as well as attacking public facilities.
April 25 is a national holiday marking Sinai Liberation Day.
The statement added that the police investigation was based on revealed that the suspects possessed firearms and Molotov cocktails.
Protests, a frequent sight in the turbulent post-uprising period, have been all but banned under a law passed months after President Abdel-Fattah al-Sissi, then head of the armed forces, ousted Islamist president Mohammed Morsi in 2013.
Authorities appear to have been roiled by a hundreds-strong demonstration outside the building on April 15 in protest of a plan to hand over two strategic Red Sea islands to Saudi Arabia.
Attempts to repeat the demonstrations on April 25 were foiled when security forces blocked off the syndicate building and broke up two small protests in western Cairo with tear gas, making more than 700 arrests, according to rights activists.
On that occasion, the syndicate said that government supporters accompanied by men in police uniform had attempted to storm its headquarters.