Police are to question Anders Behring Breivik again to follow up new leads on the Norwegian massacre and bombing.
It will be the second interrogation for Mr Breivik, 32, who admits carrying out the attacks that killed 76 people.
He has been in solitary confinement since his court appearance on Monday.
The BBC reports that police specifically want to talk to Mr Breivik about his claims that there are two other cells active in Norway.
Despite the fears, Norwegian authorities have said they believe Mr Breivik acted alone.
One week after the killings, Norway's leaders will join bereaved relatives for a memorial service in the capital Oslo.
The service has been organised by the youth movement of the Norwegian Labour party, which was the target of the shootings on Utoeya island.
The police have called off their search of the island but continue to drag the surrounding lake for remains.