The funerary site, uncovered eight meters below ground in Minya, a province about 250 km (150 miles) south of Cairo, contained limestone and clay sarcophagi, animal coffins, and papyrus inscribed with Demotic script.
The burial chamber was first detected last year by a team of Cairo University students using radar.
The mummies have not yet been dated but are believed to date to Egypt's Greco-Roman period, a roughly 600-year span that followed the country's conquest by Alexander the Great in 332 BC, according to Mohamed Hamza, a Cairo University archaeology dean in charge of the excavations.
Egypt is hoping recent discoveries will brighten its image abroad and revive interest among travelers that once flocked to its iconic pharaonic temples and pyramids but which have shunned the country since its 2011 political uprising.
Salah Al-Kholi, a Cairo University Egyptology professor who led the mission, said as many as 32 mummies may be in the chamber, including mummies of women, children and infants.
Archaeologists have excavated a slew of relics in recent months that include a nobleman's tomb from more than 3,000 years ago, 12 cemeteries that date back about 3,500 years, and a giant colossus believed to depict King Psammetich I, who ruled from 664 to 610 BC.
Tourism Minister Yehia Rashed said last month the new finds could boost tourist arrivals this year to about 10 million, an improvement from the 9.3 million visitors that came in 2015 but still far below the 14.7 million from 2010. No 2016 figure is yet available.
The tourism sector, a crucial source of hard currency, has struggled to regain ground amid a growing number of militant attacks, including two Islamic State church bombings last month.