Police in Norway were alerted to mass murderer Andres Behring Breivik as far back as March, it emerged today.
Security services were alerted to a suspicious chemical purchase by Breivik but failed to investigate further.
Officials said that Breivik paid 120 kroner (€20) for an undisclosed product from a Polish chemical firm.
The purchase set off an alert because the company was already under scrutiny.
However, the transaction was legal and without additional information, police couldn't investigate further.
In his manifesto, Breivik describes a purchase of sodium nitrite from Poland, saying he "was concerned about customs seizing the package".
The revelation fuelled further criticism of the way police reacted.
•They took 90 minutes to arrive at the island retreat after the first shots were heard.
•Survivors who called emergency services reported being told to stay off the line unless they were calling about the Oslo bombings.
•The entire Oslo helicopter crew had been sent on holiday and thus could not be mobilised to the scene.
•They dramatically overcounted the number of people killed in the shooting spree on Utoya (86 instead of 68) after counting some bodies twice.
By contrast, Breivik, who donned a police uniform as part of a ruse to draw campers to him, appeared in total control during the island rampage, police official Odd Reidar Humlegaard said.
"He's been merciless," Mr Humlegaard said.
Breivik was being in solitary confinement today after calmly telling a court that two other cells of collaborators stood ready to join his murderous campaign.
The mass murderer told authorities he expects to spend the rest of his life in prison.
Declaring he wanted to save Europe from "Muslim domination", he entered a plea of not guilty yesterday that will guarantee him future court hearings and opportunities to address the public, even indirectly.
Norway has been stunned by the attacks and riveted by Breivik's paranoid and disturbing writings.
Hundreds thronged the courthouse, hoping to get their first glimpse of the man blamed for the deaths of 76 people -- lowered from 93. At one point, a car drove through the crowd and onlookers beat it with their fists, thinking Breivik might be inside.
Tens of thousands of Norwegians also defied his rhetoric of hate to gather in central Oslo to mourn the victims and lay thousands of flowers around the city.
Police believe Breivik (32) acted alone, despite his grand claims in a 1,500-page manifesto that he belonged to a modern group of crusaders. But they have not completely ruled out that he had accomplices.
Judge Kim Heger ordered Breivik held for eight weeks, including four in isolation, noting his reference to "two more cells within our organisation".
Meanwhile, Breivik's estranged father said he wished his son had killed himself instead of unleashing his rage on innocent people.
The outpouring of emotion stood in stark contrast to what prosecutor Christian Hatlo described as Breivik's calm demeanour at the hearing, which was closed to the public over security concerns and to prevent a public airing of his extremist views.
Authorities say Breivik used two weapons during the island attack -- both bought legally, according to his manifesto. A doctor treating victims said the gunman used illegal "dum-dum"-style bullets designed to disintegrate inside the body and cause maximum internal damage.
While 21 years is the stiffest sentence a Norwegian judge can hand down, a special sentence can be given to prisoners deemed a danger to society who are locked up for 20-year sentences that can be renewed indefinitely.