A third round of ground penetrating radar (GPR) scanning is underway inside the burial chamber of King Tutankhamun, Egypt's Ministry of Antiquities announced today, as part of an effort to answer a question that has long intrigued and stumped researchers: Are the walls of the famous tomb hiding other chambers—perhaps another royal burial concealed for more than 3,300 years?

Ever since archaeologist Howard Carter discovered the treasure-packed tomb in Luxor's Valley of the Kings in 1922, experts have believed the space to be strangely small for a pharaoh. Various theories about the tomb have been proposed over the decades, but in 2015 Egyptologist Nicholas Reeves suggested an astounding possibility: The north and west walls might conceal the mummy—and fabulous possessions—of Tut’s stepmother, the legendary beauty Queen Nefertiti.

What King Tut’s tomb is hiding Stairway Scientists are investigating whether there are hidden chambers behind the north and west walls of King Tut’s tomb. 25 feet Treasury Antechamber Burial chamber Annex Hidden room? NORTH Hidden room? NG STAFF PHOTO: Kenneth Garrett SOURCES: THEBAN MAPPING PROJECT, Ministry of State for Antiquities What King Tut’s tomb is hiding Scientists are investigating whether there are hidden chambers behind the north and west walls of King Tut’s tomb. Stairway 25 feet Treasury Antechamber Burial chamber Annex Hidden room? NORTH Hidden room? NG STAFF PHOTO: Kenneth Garrett SOURCE: THEBAN MAPPING PROJECT. Ministry of State for Antiquities

Two previous scans of the burial chamber, conducted in 2015 and 2016, varied in their results and were determined inconclusive. A third non-invasive GPR scan was commissioned by Egypt’s Minister of Antiquities Khaled El Enany following the recommendation of experts who met in 2016 to study the results of the previous scans. This latest investigation, conducted under the direction of the Polytechnic University of Turin, aims to resolve those results and verify whether or not there are voids behind the walls.

Intriguing Clues

Reeve’s idea was prompted by a highly detailed 3D scan of the tomb conducted in 2009 by the firm Factum Arte, which was tasked with building an exact replica of the tomb for tourists to visit. When Reeves studied the scans of the north and west walls, he believed he saw traces of openings that had been bricked up and plastered over. Those features could help explain two other puzzling features.

In 1984 Egyptologist Gay Robins published a paper about the proportions of the figures painted on the walls of the burial chamber. On the north wall they followed a 20-square grid, but on the other three walls they followed an 18-square grid. Robbins thought that might have been the result of the rushed preparation of the tomb, which could have involved separate teams of painters trained in two different traditions. But what if the walls had been painted at two different times—after one burial was sealed, and then again when another burial was added some years later?

Experts from the Getty Conservation Institute in 2012 noticed something else that was strange. The background of the north wall was originally painted white but later repainted yellow to match the other three walls. Did the white background date to the first burial, and the repainting to the time of Tut?

When Mamdouh El Damaty, Minister of Antiquities at the time Reeves put forward his theory, took a close look at the north wall, he saw another irregularity in one area—a clear difference between two wall treatments. The upper part of that area displayed paint on bare stone, but the lower part was paint on smeared plaster.

The collection of evidence was convincing enough for El Damaty to approve infrared thermography of part of the north wall in early November 2015. The imaging technique detects variations in surface temperatures, which presumably would be different for a solid limestone wall and one concealing a room, if there was one. The imaging revealed tantalizing temperature differences on the north wall.

Later that month, Japanese radar specialist Hirokatsu Watanabe used GPR to peer behind the tomb walls. The results were sensational and made headlines around the world. Watanabe thought he could see chambers behind the north and west walls, as well as artifacts of metal and organic materials.

But many Egyptologists and GPR experts had serious doubts about the results of that survey, so a second round of GPR was launched in March 2016. This time National Geographic engineers carried out the work.

Expectations were huge, but the results were puzzling. The survey was designed to look for walls of the same thickness that Watanabe had seen, but it didn’t pick up anything like that—or any hint of voids to the north or west of Tut’s burial chamber.

The results of those two probes brought the investigation to a standstill. The project needed a tiebreaker.

Results: Yes or No?

The third GPR survey will leave no stone unturned by radar technology, with plans calling for several four-hour sessions of scanning. The results of the completed work should hopefully provide the final answer on whether there are hidden chambers or not. Scientists caution, however, that the GPR scans can only detect “anomalies” in the rock, and further research will be required to determine if any anomalies are in fact hidden rooms.

The current project, a joint scientific mission between Egypt and Italy, is being coordinated by Italian physicist Francesco Porcelli from the Polytechnic University of Turin in partnership with the University of Turin and three private companies, Geostudi Astier, 3DGeoimaging, and Terravision.

“I'm privileged to be given this opportunity, and I'm privileged to be coordinating such a great team,” Porcelli told National Geographic during a break between scanning sessions on Thursday evening.

The GPR team works through the night, after the Valley of the Kings and Tut's tomb are closed to tourists. The researchers carefully navigate their high-tech equipment in the tight spaces of the burial chamber under of the supervision of Egyptian officials, careful to ensure that the radar antennas scan as close as possible to the wall surfaces without disturbing the priceless paintings of the 3,300-year-old tomb.