Ayedi said Egypt would soon announce an additional significant find near the Lahun pyramid, once covered by slabs of white limestone, showing the site could date back to an earlier era thousands of years before previously thought.
"The prevailing idea was that this site has been established by Senusret II, the fourth king of the 12th dynasty. But in light of our discovery, I think we are going to change this theory, and soon we will announce another discovery," he told reporters.
He said teams had made a discovery dating to before the 12th dynasty, but gave no details on what it was and said an official announcement could be made within days.
Ayedi said he had wanted to excavate at Lahun, Egypt's southernmost pyramid, because he was not satisfied with the result of the first excavation there in the 19th century, saying it did not match the significance of the site.
"The size of the site is huge. So I thought that we could unearth a lot of elements in this site. At the beginning of the excavation, I thought that we may rewrite the history of the area, and I was right," he said.
Archaeologists gave journalists a rare tour of the ancient burial site Sunday, which is next to the nearly four millennia old pyramid of Pharaoh Sesostris II.
"At the beginning of the excavation I said that we may rewrite the history of the site, and I was right," said Abdel-Rahman el-Ayedi, the deputy secretary of Egypt's Supreme Council of Antiquities who oversaw the dig.
Three slim wooden sarcophagi believed to be holding female mummies were laid out in one of the tombs. The innermost coffins were painted to resemble the deceased using blue, yellow, rust and black dyes.
In another tomb, workers slowly removed the lid of one inscribed with hieroglyphic prayers to reveal a colorful mummy case that el-Ayedi said belonged to a woman named Isis Her Ib, the daughter of one of Illahun's mayors nearly 4,000 years ago.
Not much was known about who used the ancient necropolis. El-Ayedi said some of the tombs were just 2,800 years old, while others were from the Middle Kingdom, which dates back 2061-1786 B.C.
Some had a single burial shaft, while others had upper and lower chambers. A funerary chapel with an offering table, painted masks, pottery, statues and protection charms known as amulets were also found at the site, el-Ayedi said.