New research into the Turin Shroud has added to the mystery surrounding the controversial artefact.
Turin Shroud from front and back
A second ghostly image of a man's face has been discovered on the back of the linen, according to a report published by London's Institute of Physics.
The delicate 14ft-long linen sheet is believed by some to be the cloth in which Jesus was wrapped after being taken down from the cross.
It has been dismissed by others as an elaborate hoax.
The back of the shroud has rarely been seen as it was hidden beneath a piece of cloth sewn on by nuns in 1534, after it was damaged by fire.
But the back surface was exposed during a restoration project in 2002.
A professor at Italy's Padua University, Giulio Fanti, thought he saw a "faint image" in the photographs from this project and decided to investigate it further.
"Though the image is very faint, features such as nose, eyes, hair, beard and moustaches are clearly visible," he said.
"There are some slight differences with the known face. For example, the nose on the reverse side shows the same extension of both nostrils, unlike the front side, in which the right nostril is less evident."
Professor Fanti has dismissed claims that the image on the back confirms that the shroud is a fake - with paint soaking from the front to the back.
"This is not the case of the shroud. On both sides, the face image is superficial, involving only the outermost linen fibres," he said.
"It is extremely difficult to make a fake with these features."
Shrouded in mystery
These findings are just the latest in the controversy which has dogged the cloth since it was first photographed more than 100 years ago.
Carbon-dating tests carried out in 1988 suggested the shroud was a fake.
In 1988 the shroud was revealed as a fake
In the 1988 study, scientists from three universities concluded that the cloth dated from some time between 1260 and 1390, and that it was not the burial cloth wrapped around the body of Christ.
That led to the humiliating spectacle of the then Cardinal of Turin, Anastasio Alberto Ballestrero, admitting the garment was a hoax.
But since then, some doubt has been cast on the carbon-dating techniques.
In 1997, a Swiss archaeologist who spent 16 years studying the shroud said new tests had proved its authenticity "beyond all reasonable doubt".