Polish officials say police have arrested 19 people on suspicion of producing and possessing bomb-making materials and providing them to confessed Norwegian mass murderer Anders Behring Breivik.

Poland's Internal Security Agency made the announcement Thursday and said the arrests were part of a wider investigation by Norwegian police.

Polish police were able to locate many of Breivik's suppliers due to his 1,500-page manifesto posted on the Internet, in which he described buying Polish fuses to detonate a bomb outside of Norway's government headquarters in Oslo.

During the investigation, Polish authorities searched some 85 homes.

Earlier Thursday, Norwegian authorities said they were allowing Breivik out of solitary confinement as he awaits trial for murdering 77 people in July.

Police prosecutor Christian Hatlo said investigators are increasingly confident that Breivik did not have any accomplices when he opened fire at a youth camp outside of Oslo and set off a bomb in the capital's government district.

Hatlo says for that reason authorities will not request a judge to extend the 32-year-old's solitary confinement when it expires next Monday. However, Breivik will remain separate from other prisoners for his own safety.

Since his July 22 arrest, Breivik has been held in solitary confinement following his claim that there were up to 80 cells in Europe with militant anti-Islamic ideals like his own ready to strike. Police say they have found no evidence that any of those cells exist.

Norwegian police have asked authorities in 20 nations to bring in people for questioning to find out more about Breivik's contacts and purchases of bomb-making materials.

Even though Breivik confessed to the killings, his lawyer says he denies criminal responsibility because he believes the massacre was needed to save Norway and Europe from an influx of Muslims and to punish politicians for embracing multiculturalism.