Police press officer Roar Hanssen said: "We have some names and also some groups we are investigating. They came from Paul Ray, and also from Breivik and also from other things we have been investigating."
Breivik, 32, admitted killing 77 people last month when he detonated a truck bomb outside government offices in Oslo, and then went on a shooting spree at a youth camp at Utøya, 25 miles away.
He was questioned again on Wednesday and prosecutor Paal-Fredrik Hjort Kraby said officers focused on Breivik's manifesto, his alleged links to a group called the Knights Templar and potential ties to the UK.
Hanssen said: "A lot of people are mentioned in Breivik's manifesto and we, of course, want to speak to them and there are some links to the UK. I don't know if there are specific areas they are from but there are some rightwing groups."
Ray was interviewed last week after claims he may have been the "mentor" mentioned by Breivik in his "manifesto", posted online shortly before he carried out the killings on 22 July.
Ray, who wrote his blog under the name Lionheart, has said it appeared Breivik drew inspiration from some of his ideas and writings, but he has repeatedly denied any link, saying he never met Breivik and was horrified by the killings. He said he travelled to Norway to "clear his name".
Breivik wrote that he attended the founding meeting of the Knights Templar Europe "military order" in London in 2002 where he met a "mentor" who used the pseudonym Richard, after Richard the Lionheart. He signed the 1,500-page document with an anglicised version of his name and datelined it London 2011.
Breivik also repeatedly praised the English Defence League, saying he had 600 EDL supporters as Facebook friends and had spoken with members and leaders. The EDL has condemned the killings and has denied any official contact with Breivik, insisting it is a peaceful, non-racist organisation opposed to extremism.
Kraby said Norwegian police did not have evidence that Breivik had accomplices, but "did not rule out the possibility."
Norwegian officers are now deciding whether to carry out the interviews in the UK or in Norway.
Hanssen said: "We can ask for help from the British police. It is not decided what we will do yet but these are possibilities."