If convicted, the three reporters, all women, could face from six months to two years in prison, as well as fines of up to 300,000 Egyptian pounds ($9,810), Mada Masr said in an article about the case.
There was no immediate comment from judicial authorities.
The case stems from a Mada Masr article reported by the three journalists and published last year, which said a state inquiry had implicated members of the Nation's Future party in "gross financial misconduct".
The party, which strongly supports President Abdel Fattah al-Sisi and is a dominant force in Egypt's parliament, denied the report and its members and followers submitted hundreds of complaints against the journalists.
Mada Masr is one of the few independent outlets struggling to operate in Egypt after a far-reaching crackdown on political dissent and curbs on independent civil society.
Its website is blocked within Egypt and its Cairo offices were raided in 2019.
Its editor, Lina Attalah, has been charged with founding a website without a licence. Mada Masr says it has attempted since 2018 to obtain a license under a new law regulating the press, but has received no response to repeated inquiries.
Media watchdog Reporters Without Borders ranks Egypt 168th out of 180 countries surveyed in its press freedom index, and says 24 journalists are currently jailed in the country.
($1 = 30.5800 Egyptian pounds)
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