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The structure "seems to have been filled with sand, which means it was backfilled after it was constructed," the team wrote in the study.
"This anomaly extends to 3.5–10 m in depth and over a horizontal area of 10 m by 10 m," they explained.
Understanding the composition and dimensions of the anomaly is important for predicting whether it is man-made or just a naturally occurring phenomenon.
"We believe that the continuity of the shallow structure and the deep large structure is important," scientists said.
"From the survey results, we cannot determine the material causing the anomaly, but it may be a large subsurface archaeological structure."
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And more studies of the area are already underway, he said.
As to the question of whether the anomaly is natural or not, Sato had little doubt.
"The shape is too sharp" for it to be an environmental occurrence, he said.
The area had previously gone explored due to a lack of superstructures above ground Credit: Sato, M. et al., Archaeological Prospection Scientists are beginning to excavate the area now to investigate the 'anomaly' Credit: Sato, M. et al., Archaeological Prospection NEW HORIZONS IN RESEARCH Egyptologists were fascinated by the find too.
The newly found underground passage stands out from other studies because there is no evidence of a standing structure above ground.
Typically, most underground chambers in the Giza complex have been found underneath other ruins, Peter Der Manuelian, a professor of Egyptology at Harvard University who was not involved in the study, told Live Science.
"It's an interesting area, one that has avoided exploration due to the absence of superstructures," he said.
He said there are other L-shaped structures at Giza, now known to be offering chapels, but they are usually aboveground.
"I'm not sure just what this anomaly represents yet, but it is certainly worthy of further exploration," he added.
A brief history of Ancient Egypt Here's everything you need to know...
The Ancient Egyptians were an advanced civilization who at one point owned a huge portion of the globe The civilization began about 5,000 years ago when ancient humans began building villages along the River Nile It lasted for about 3,000 years and saw the building of complex cities centuries ahead of their time – as well as the famous Great Pyramids The Ancient Egyptians were experts at farming and construction They invented a solar calendar, and one of the world’s earliest writing systems: The hieroglyph The Egyptians were ruled by kings and queens called pharaohs Religion and the afterlife were a huge part of Ancient Egyptian culture. They had over 2,000 gods Pharaohs built huge elaborate tombs to be buried in, some of which were pyramids – at the time among the largest buildings in the world The Egyptians believed in life after death, and important people’s corpses were mummified to preserve their bodies for the afterlife The Ancient Egyptian empire fell due to a mix of factors, including wars with other empires and a 100-year period of drought and starvation