Stolen 'Scream' back on display

(CNN) -- Edvard Munch's masterpiece, "The Scream," went back on display Friday in Oslo, Norway -- four years after thieves pulled the painting from its frame in a daring armed robbery.

The Munch Museum is displaying "The Scream" alongside another work that thieves stole in 2004. Police arrested three men in the case in 2006 and recovered the paintings that August.

The museum displayed the painting for five days after its recovery. Then workers began to restore it. Friday is the first time the restored paintings are back on display.

The worst damage to "The Scream" was a stain in the lower-left corner, the museum said. The cardboard support for the painting also had started to split along the edges and come away from the wood underneath.

The painting suffered scratches to the paint -- in come cases exposing the cardboard underneath -- and lost paint in some places, the museum said. It also became "considerably" dirtier, it said.

The museum described a "painstaking and time-consuming process" to restore "The Scream" and another stolen painting.

"Even after the conservation, the paintings are marked by the damages that occurred in connection with the robbery," said Ingebjorg Ydstie, chief curator at the museum. "But the artistic value of the paintings has not been reduced."

Armed, masked robbers stole the priceless paintings in broad daylight in August 2004 as museum visitors watched in shock. The works had not been guarded, even though "The Scream" is one of the most famous paintings in the world and was stolen from Oslo's National Museum of Art in 1994.

After the theft, the Munch Museum closed for nearly a year to update its security measures, which now include X-ray scanners, metal detectors, and security gates for visitors, said Jorun Christoffersen, head of marketing at the museum.

"All our paintings now are protected with security glass and they're very properly attached to the walls, and of course we have guards and extra surveillance," she told CNN. "We consider the paintings as safe to exhibit now."

The Munch Museum's "Scream," believed to date from 1910, is one of two painted versions created by Munch. The other is at the National Museum of Art, Architecture and Design, also in Oslo.