The man behind last week's twin attacks that killed 76 people was investigated in March for a purchase of chemicals, but the probe was dropped, Norwegian police said on Monday.
Anders Behring Breivik came to police's attention because of a purchase from a Polish business selling chemicals, but the incident was judged too insignificant to warrant a follow-up, Norwegian Police Security Service (PST) head Janne Kristiansen said.
"In March, we received ... a list of 50-60 names and his name was on it because he spent 120 krone (15 euros or 22 dollars) at a business in Poland," the head of the PST, which reports directly to the ministry of justice, told Norway's public television channel NRK.
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"This business was under surveillance because it was selling other chemical products."
The PST receives "a lot of intelligence" on "a lot of people," she said.
"We don't have the right to put people's names on the register just like that but we checked if we had anything on these people, if any of them could be connected to any other intelligence we had but we had absolutely nothing on Behring Breivik."
"He lived a life that was incredibly respectful of the law," she said.
Poland's security service said earlier Monday that Behring Breivik had ordered chemicals from a Polish firm whose owner they have questioned since the massacre at Norway's request. No arrests were made at the firm.
Pawel Bialek, deputy head of the ABW internal security agency, said the chemicals purchased did not appear to have been of capital importance to his plans, and said the Norwegian had also placed larger orders from other countries.
Bialek said the chemicals purchased were similar to those described in a 1,500-page manifesto Behring Breivik had posted on the Internet prior to Friday's massive car bombing and subsequent mass shooting.
According to copies of the manifesto still available online, he ordered 300 grammes of sodium nitrate in December 2010 at a cost of 10 euros (14 dollars), noting that it could be used as the primary charge in an explosive device.
He said he had prepared a cover story that he planned to use it to cure moose meat -- it was a common method.
Behring Breivik also wrote that he regretted having placed his orders because he feared the company would be put under surveillance by intelligence services.
