Norwegian police said they will question Anders Behring Breivik again today after new information emerged relating to his killing spree, as prosecutors warned he would not go on trial before 2012.
Friday's interrogation will be only the second time police have quizzed the far-right extremist since Saturday, the morning after his shooting rampage on Utoeya island and the bomb blast in downtown Oslo that together killed 76 people.
The six-day search for bodies on the island has now ended, and police said they were increasingly certain he acted alone.
Overnight the names of another 24 of his victims were released, setting the confirmed total by police at 41.
Police official Paal-Fredrik Hjort Kraby said officers will question Behring Breivik on "the information received over the last few days - which is a lot," although he did not reveal the nature of the information.
European counter-terrorism experts met in Brussels to look at wider lessons that can be drawn from the attacks, and an Oslo gun club said Behring Breivik had been a member since 2005.
But as the depth and complexity of the investigation spread, the Norwegian king's prosecutor general Tor Aksel Busch - the country's highest legal officer - said time would be required to sift through the evidence.
"We hope that we can conduct the court trial in the course of next year," he said, adding that Behring Breivik's indictment "will not be ready before the end of the year."
The possibility that the killer had been working with anyone else was receding, officials said, despite an international intelligence probe.
That possibility "has become weaker over time," police spokesman Henning Holtaas told AFP, although "we are checking all his communications."
He did not confirm that Behring Breivik was carrying the walkie-talkie radio on Utoeya island, where he shot 68 mostly young people dead, but two witnesses have said he was.
"He was dressed like a policeman. He had all the equipment - the walkie-talkie, the arms, everything," 15-year-old survivor Jo Granli Kallset told AFP.
A functioning walkie-talkie would not reach much further than the mainland as little as half a mile away.
Locals have cast doubt on whether the device would be anything more than a prop as part of his disguise as a police officer.
Behring Breivik boasted before the attack in a 1,500-page manifesto that he was one of up to 80 "solo martyr cells" recruited across western Europe to topple governments tolerant of Islam.
Norway's intelligence service has been liaising with counterparts across Europe and in the United States but has found nothing so far to verify the gunman's claims of active cells forming a terror "organisation," made during a court hearing and in the tract.
Norway's intelligence services chief Janne Kristiansen said in an interview with AFP that the possibility the killer had acted as a "lone wolf" could make it more difficult for police to uncover his trail.
"He has done this very carefully and meticulously and so far he has succeeded in avoiding any radar, or radar of the secret services."
European Union terrorism experts meeting in Brussels warned that the bloodbath in Norway, which they said was almost "impossible to prevent", simply underlined the need for stronger European counter-terrorism action, both against "lone wolves" and all forms of extremism.
Police are still searching the waters around Utoeya and the bomb site in downtown Oslo for missing persons, although they said Thursday that the land search on the island had ended.
Officials did not revise their tolls from the two attacks. Eight people died in an initial car bomb blast in central Oslo that also sowed confusion among the police before the shooting spree.
Norwegian police on Thursday released the identities of 24 more people, aged between 14 and 30, all but one of whom were killed on Utoeya island.
The list included one Georgian, and brought the total number of confirmed dead whose names have been made public to 41.
Survivor Emma Martinovic told in a blog entry how "I heard the bastard laugh, I heard him shout 'you won't get away'," testimonials emerged to a lost generation of future Norwegian political leaders so brutally cut down.
These included Anders Kristiansen, an 18-year-old whose mother said he "dreamed of becoming prime minister since the age of five," and whose shining talent was lauded by Norwegian Foreign Minister Jonas Gahr Stoere in the national press.