A 3,300-year-old bust of Nefertiti has a stucco exterior that conceals a limestone core. (Herbert Knosowski/Associated Press)Researchers in Germany have discovered that Nefertiti, an Egyptian bust on display on Berlin's Altes Museum, has two faces.

A team led by Dr. Alexander Huppertz, director of the Imaging Science Institute at Berlin's Charite hospital and medical school, used modern medical technology — a CT scan — to look under the stucco exterior of the 3,300-year-old work.

They discovered a detailed stone carving of the face of Nefertiti that differs from the external stucco face, which has earned her a reputation as The Beauty of the Nile, according to a study published Tuesday in the monthly journal Radiology.

It is not the first time scientists have used medical technology to peek beneath the surface of the antiquity, but modern computed tomography, or CT, gives a more detailed picture of the stone underneath than earlier techniques.

The Nefertiti bust consists of a limestone core covered in layers of stucco of varying thickness.

"Until we did this scan, how deep the stucco was and whether a second face was underneath it was unknown," Huppertz said. "The hypothesis was that the stone underneath was just a support."

Instead, it turned out to be a skilfully rendered artwork.

A CT scan shows slight differences on the face underneath, including creases around the mouth and eyes and a bump on the nose of the stone version. (Radiological Society of North America/Associated Press) The scan reveals that the stone carving of her face had creases at the corners of the mouth and a bump on the nose that don't appear in the stucco version. The stucco artist also appears to have enhanced the height of her cheekbones.

"Changes were made, but some of them are positive, others are negative," Huppertz said.

May have been powerful ruler

Nefertiti was the wife of Pharaoh Akhenaten and may have been a powerful ruler in her own right. She lived from about 1370 BC to 1330 BC.

Egyptologist Ludwig Borchardt discovered the bust in 1912 and added it to Berlin's Egyptian collection housed in a group of museums on Museum Island.

"We acquired a lot of information on how the bust was manufactured more than 3,300 years ago by the royal sculptor," Huppertz said, adding that this knowledge would help in preserving the work.

The museum refused to return the bust to Egypt for an exhibit in 2007, saying it was too fragile to travel.

Egyptologists, including experts at the British Museum in London, are now studying the differences, trying to pinpoint why someone in a position of power would have ordered them.

Huppertz said the Pharoah himself may have ordered the wrinkles smoothed on his wife's face to conform with conventional standards of beauty in 14th century B.C.

"It is possible that the bust of Nefertiti was commissioned, probably by Akhenaten himself, to represent Nefertiti according to his personal perception," he said.

The bust, currently on display at the Altes Museum, will move into the Neues Museum when it reopens in October after a restoration by British architect David Chipperfield.