By Aidan LewisCAIRO (Reuters) -A hidden corridor nine metres (30 feet) long has been discovered close to the main entrance of the 4,500-year-old Great Pyramid of Giza, and this could lead to further findings, Egyptian antiquities officials said on Thursday. The Great Pyramid was constructed as a monumental tomb around 2560 BC during the reign of the Pharaoh Khufu, or Cheops. It was possible the pharaoh had more than one burial chamber, Waziri added. Scientists detected the corridor through cosmic-ray muon radiography, before retrieving images of it by feeding a 6mm-thick endoscope from Japan through a tiny joint in the pyramid's stones. In 2017, Scan Pyramids researchers announced the discovery of a void at least 30 metres long inside the Great Pyramid, the first major inner structure found since the 19th century.