A Norwegian police stands at a farm rented by Anders Behring Breivik in the small rural region of Rena, 150 km (93 miles) north of Oslo, July 27, 2011. The Norwegian anti-Islamic zealot who killed 76 people claims he worked with others, but finding far-right groups in their mainly online haunts will be tough for police who for years gave Islamist militants top priority. Police and experts point to the Internet's role in spreading the racist material that shaped killer Anders Behring Breivik's extreme views, but also highlight the difficulty in policing dynamic online forums without undermining civil liberties. Reuters

At the farm rented by Anders Behring Brievik, Norwegian police detonated a cache of explosive materials. Authorities have not disclosed the amount of bomb-making material they found, but said they said they blew up the stash in a controlled environment.

Breivik is believed to have built the bomb that exploded on Friday at government headquarters in Oslo, killing seven, from the farm 100 miles north of Norway's capital. Police found a significant amount of fertilizer, according to reports, the main ingredient in many home-made explosive devices.

Posing as a farmer, Breivik reportedly bought fertilizer from a local store without incident.

According to his manifesto, Breivik had been planning his attack for up to nine years before he went on his rampage Friday. He outlined detailed instructions on how to attack government targets, believing that he was a crusader in a war against a Marxist-Islamic conspiracy.

He also detailed the costumes and ranks of his supposed army. Breivik claimed in the 1,500-page document, as well as in court, that he was involved with a militant group -- linked to the Knights Templar -- and was just one of many European cells fighting against the forces of "Eurabia."

Police are currently investigating the claim and looking at Breivik's links to European far-right political parties and extremist groups. Norwegian authorities believe that Breivik's claims are unsubstantiated and possibly delusional. It is now assumed that Breivik enacted his plan alone.

Officials are following every clue nonetheless.

"We feel that the accused has fairly low credibility when it comes to this claim but none of us dare to be completely dismissive about it either," a source close to the police investigation told Reuters.

"I can tell you, at this moment in time, we don't have evidence or we don't have indications that he has been part of a broader movement or that he has been in connection with other cells or that there are other cells," domestic intelligence chief Janne Kristianse said Tuesday.

Police are also investigating the existence of Breivik's "survivor's kit." In the manifesto, Breivik said he hid weapons, ammunition, food and money to help him break out of prison, should he be captured alive.