Mostafa Waziri, secretary-general of the Supreme Council for Antiquities, told reporters that the discovery was the largest in the country for more than a century.
It is the first Sarglager discovered by an Egyptian mission after years of archaeological excavation.
"The last was in 1891, [led by] foreigners in 1881, [also] foreigners, but … 2019 is an Egyptian discovery," said Waziri. "That's an indescribable feeling, I swear to God."
The discovery was unveiled in front of Hatshepsut Temple in the Valley of the Kings in Luxor.
Egyptian Antiquities Minister Khaled El-Enany described the 3,000-year-old coffins buried in the Al Asasif Cemetery as "Exceptionally well preserved, exceptionally well colored."
They contained the mummified remains of both men and women and two children believed to be middle-class, Waziri said.
While the mummies were found completely wrapped in cloth, their genders could be identified by the shape of the hands on the casket. Coffins carved with open hands meant they were female, and when the hands were clenched in fists, according to Waziri, they held men.
According to archaeologist Zahi Hawass, finding coffins of a child is rare. The discovery of two animals has aroused great interest "worldwide".
The coffins were sealed, stacked on top of each other and placed in two rows about a meter below the sand, he said.
They are adorned with intricate carvings and patterns, including Egyptian deities, hieroglyphics, and scenes from The Book of the Dead, a series of spells that allowed the soul to navigate through the hereafter. Names of the dead are also engraved on some coffins, Hawass said.
The inscriptions are particularly unique, as the colors remained alive, although the coffins were buried for millennia. This is because, according to Waziri, the ancient Egyptians used natural colors of stones such as limestone, red oak and turquoise mixed with egg white.
After painting, egg yolk was mixed with candle wax and painted over the coffin to give it a natural glow that is still visible. he said.
Officials said the first coffin was discovered because its head was partially uncovered. As they continued to dig, 17 more coffins were found. After these coffins were excavated, the archaeologists discovered another 12.
According to Waziri, the coffin cache was most likely hidden to keep grave robbers away from them.
Hawass told reporters at a press event that the discovery reveals important details about ancient Egyptian funerary rights, such as how they respected the dead, regardless of gender or age.
"This will enrich our knowledge as an Egyptologist about belief in life after death," Hawass said.
The mummies are restored before being moved to a museum of ancient Egyptian artifacts near the Giza Pyramids. The coffins receive their own exhibition.
"They are relocated to the Grand Egyptian Museum, which will open in late 2020 as a new surprise for our visitors," said El-Enany.