Police in Norway said they are looking for eight new suspects thought to have been involved in the theft of Edvard Munch's iconic painting The Scream.
The Scream is also known by another name, The Cry
"We forsee new arrests", said Iver Stensrud, the inspector in charge of the investigation.
The painting was stolen from Oslo's Munch Museum a year ago, when thieves held up staff with a gun and stole the artwork from the wall.
Five others have already been arrested, with three remaining in custody.
The two other people, who are thought to have played a minor role in the theft, have since been released.
The Scream, along with another Munch work, Madonna, remains missing.
In June, the authorities in the Norwegian capital offered a reward of two million Kroner (£170,000) for information leading to the paintings' return.
The artworks have been valued at more than £10m.
"We're still hopeful, but we are no longer confident. The chances of finding the paintings diminish with time and already a lot of a time has passed," said Munch Museum spokesman Jorunn Christoffersen.
The Scream was taken along with The Madonna (pictured)
Experts are concerned that the paintings may have been destroyed as they would have been too easily identifiable to be sold on the open market.
The Munch museum, which holds 1,100 of his works, remained closed for 10 months following the thefts, reopening in June.
A pastel version of The Scream has been hung in its place, while airport-style security has been introduced to the museum in an effort to combat future thefts.
Munch, who lived from 1863-1944, made several versions of both The Scream and Madonna.
Earlier this month, masked thieves stole what they thought were valuable Munch paintings from an Oslo hotel, but they turned out to be worthless copies.