An international team of researchers says it has confirmed the existence of a large empty space in the pyramid of Egyptian Pharaoh Khufu by observing elementary particles known as muons.
On Thursday, the team announced its findings, which are said to be the first such discovery in 186 years, in the city of Giza near Egypt's capital Cairo.
Egyptian Minister of Tourism and Antiquities Ahmed Issa and Associate Professor Morishima Kunihiro of Japan's Nagoya University, a member of the team, attended the news conference.
The researchers said they discovered the void in the shape of a corridor stretching from near the pyramid's northern slope toward its center.
They say the space measures 2 meters in width and height, and 9 meters in length.
The team is made up of researchers from Egypt, Japan, France, Germany and elsewhere. It has been looking into the interior structure of Khufu's Pyramid since 2015. The pyramid was built about 4,500 years ago.
The team employed cosmic-ray muon radiography technology of Nagoya University and the Japan-based KEK High Energy Accelerator Research Organization. NHK has cooperated in filming video using scopes.
Muons are created when cosmic rays hit the Earth's atmosphere. Muons are tiny, so they pass through various substances. But rocks and other substances with high density tend to reduce the number of particles that pass through.
By taking advantage of this property, it is possible to see through the internal structure like X-ray photos by analyzing differences in the amount of muons that pass through buildings and other substances.
The technology has so far been used in locating volcanic magma and examining the inside of damaged reactors at the Fukushima Daiichi nuclear power plant.
In 2017, the team used the same technology to obtain data that pointed to the existence of another large void about 30 meters long inside the pyramid, adding to expectations for more new discoveries.
Archaeologist Kawae Yukinori, associate professor of Nagoya University's Institute for Advanced Research, says the latest discovery is historic in the study of pyramids.
He said it showed the 30-meter-long void, which the muon radiography detected in 2017, also exists without doubt. He said there is a possibility that similar empty spaces could be found in other pyramids in Giza.