Egyptian officials now say they are "90% sure" that there is a hidden chamber in King Tutankhamun's tomb.
The Antiquities Ministry said it had carried out scans to gather more information about the theory.
Archaeologist Nicholas Reeves believes Tutankhamun's remains may have been rushed into an outer chamber of what was originally Queen Nefertiti's tomb.
The remains of Tutankhamun, who may have been her son, were found in 1922. He died 3,000 years ago aged 19.
"Clearly it does look from the radar evidence as if the tomb continues, as I have predicted," Dr Reeves said at a press conference with the Egyptian Antiquities Minister Mamdouh al-Damati on Saturday, AFP reports.
"The radar, behind the north wall [of Tutankhamun's burial chamber] seems pretty clear. If I am right it is a continuation - corridor continuation - of the tomb, which will end in another burial chamber," he said.
Mr Damati said the scans would now be sent to Japan for further analysis.
Dr Reeves developed his theory after the Spanish artistic and preservation specialists, Factum Arte, were commissioned to produce detailed scans of Tutankhamun's tomb.
The scans were then used to produce a facsimile of the 3,300-year-old tomb near the site of the original Valley of the Kings in Luxor.
While assessing the scans last February, Dr Reeves spotted what he believed were marks indicating where two doorways used to be.
The archaeologist from the University of Arizona says he believes Nefertiti may lie inside.
Tutankhamun's tomb was the most intact ever discovered in Egypt. Close to 2,000 objects were found inside.
But its layout has been a puzzle for some time - in particular, why it was smaller than those of other kings' tombs.
Dr Reeves believes there are clues in the design of the tomb that indicate it was designed to store the remains of a queen, not a king.
His theory has yet to be peer-reviewed and leading Egyptologists have urged caution over the conclusion.
Who was Queen Nefertiti?
- The name Nefertiti means "a beautiful woman has come"
- She was queen of Egypt and wife of Pharaoh Akhenaten during the 14th century BC
- She and her husband established the cult of Aten, the sun god, and promoted a new style of Egyptian artwork
- It is thought the couple married when Nefertiti was about 15 and had six daughters and a son
- Some theories hold that Nefertiti was the mother of King Tutankhamun