Police in Oslo are setting up a special unit to investigate the twin attacks that killed 77 people.
Anders Behring Breivik has confessed to setting off a bomb in the capital and to a massacre at an island youth camp. But, many unanswered questions remain, including how Breivik financed the attacks and with whom he was in contact.
Breivik has claimed to belong to a shadowy group of modern-day crusaders against Islam, with cells all over Europe.
Police attorney Paal-Fredrik Hjort Kraby said Wednesday that police are particularly interested in any bank accounts Breivik may have opened.
The attacks drew attention to the Nordic region's far-right parties that call for strong limitations on immigration. Breivik once was a member of Norway's far-right Progress Party.
Similar parties in Sweden, Denmark and Finland have taken pains to denounce Breivik's actions while maintaining their positions on immigration.
On Wednesday, the head of Denmark's People's Party, Pia Kjaersgaard, said in her annual summer news conference that "We must not put a lid on ourselves. We must keep our freedom of speech."