Thieves who stole Edvard Munch's The Scream, one of the world's most famous images, may have damaged the painting so badly it cannot be completely repaired, say experts.

The painting and another Munch masterpiece, Madonna, were recovered by police in August, two years after they were stolen from Oslo's Munch Museum by masked gunmen in a brazen daylight heist on Aug. 22, 2004. Police have refused to say how they recovered the artworks, or where they had been for two years.

After an extensive study, museum experts on Friday are to give Oslo police a 200-page report which, among other things, expresses concern about moisture damage to a large part of The Scream.

"Water has been absorbed by one corner of the paper board, and there is abrasion damage on the lower part of the painting," Museum curator Ingebjoerg Ydstie told the TV-2 network late Wednesday. "We have a large swath that is very visible."

She said the museum was still assessing what to do about the damage, and whether can be fixed, but that no decision had been made.

"There are types of damage we can't do anything about," museum restoration expert Anne Milnes told TV-2. The Scream is probably the best known of Munch's emotionally charged works and was a major influence on the Expressionist movement. In four versions of the painting, a waif-like figure is apparently screaming or hearing a scream. The image has become a modern icon of human anxiety.

Museum spokeswoman Jorunn Christoffersen on Thursday said they would not comment further until after the report had been released, but referred to a summary of the resonation efforts posted on the city-owned museums Web site. That summary said experts are still trying to determine what kind of liquid caused the moisture damage in the lower left corner of the painting.