Scientists announced Thursday they'd discovered a secret chamber in Egypt’s Great Pyramid of Giza. The findings were detailed in the scientific journal Nature. The mysterious chamber is just under 100 feet wide and 50 feet high and buried deep within the pyramid, just above the Grand Gallery. Scientists said they were unsure of the purpose of the room.

The discovery was made using cosmic-ray imaging, a technique that uses subatomic particles to create a 3-D image of a structure. The particles, called muons, go much deeper than x-ray scans. Muons are naturally occurring and shower the earth daily.

Mehdi Tayoubi, a co-founder of the ScanPyramids project, the non-profit organization that made the discovery spoke to reporters about the find Wednesday.

“This is a premier,” said Tayoubi, according to the Associated Press. “It could be composed of one or several structures... maybe it could be another Grand Gallery. It could be a chamber, it could be a lot of things.”

The discovery could be the first time anyone has known about the room since the pyramid was built, according to Tayoubi.

“It was hidden, I think, since the construction of the pyramid,” said Tayoubi. “No very big structure has not been discovered inside the Khufu pyramid since the Middle Ages.”

The Great Pyramid is also known as Khufu’s pyramid, after the pharaoh for whom the structure was built. The pyramid was built around  2560 B.C., and Khufu reigned from around 2509 to 2483 B.C. Khufu was thought to be a god and the 455-foot tall pyramid was the tallest man-made structure until 1300, according to Vox.

Scientists are doubtful about the discovery producing anything too tantalizing, but hope that it might offer insight into how the pyramids were built. 

“There’s zero chance of hidden burial chambers,” said Aidan Dodson, an Egyptologist at the University of Bristol in the U.K., according to Science.