"This project greatly expanded our understanding of one of the best known and significant sites from antiquity, and the methodology used can serve as a model for similar sites," Tim Whalen, director of the institute, said in a statement.

Tutankhamun, just a child when he assumed the throne, was about 19 when he died.

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His tomb, discovered in 1922 by British archaeologist Howard Carter, was hidden for millennia by flood debris that preserved it intact and protected it from tomb raiders.

Over the years humidity and dust carried in by visitors have caused damage, as have some visitors who scratched the wall paintings.

"Humidity promotes microbiological growth and may also physically stress the wall paintings, while carbon dioxide creates an uncomfortable atmosphere for visitors themselves," said Neville Agnew, the institute's senior principal project specialist.

"But perhaps even more harmful has been the physical damage to the wall paintings. Careful examination showed an accumulation of scratches and abrasion in areas close to where visitors and film crews have access within the tomb's tight space."

Conservationists also studied mysterious brown spots on some of the paintings that have baffled experts for years. They concluded they were caused by microorganisms that have since died and are causing no further damage.

They decided to leave the spots there because they have penetrated into the paint layers and removing them would cause more damage.

AP