Qvarnström told Sveriges Radio (SR) that a decision will be taken in early 2013 about whether a prosecution can be filed or whether the case should be dropped. The latter is the more likely scenario, said Qvarnström, but she did not want to go into any further detail.
"Once a decision is made I will tell as much as possible about our work, what conclusions we have drawn and what the situation looks like," she said.
It was on Saturday December 11th in 2010 that the 28-year-old Iraqi-born Swede Taimour Abdulwahab made his way to Drottninggatan in central Stockholm, at the height of the Christmas shopping season.
He carried 13 kilos of explosives in a backpack and another four kilos around his waist. Abdulwahab set off two explosions but was the only fatality of the twin blasts. Two bystanders were injured.
An FBI investigation later showed that between 30 and 40 people could have died had the suicide bombing not been botched.
In a letter, Abdulwahab wrote that his purpose was to kill "your children, daughters, brothers and sisters".
On March 8th 2011 Scottish police arrested Nazzedine Menni, a 30-year old man, in Glasgow in connection with the Stockholm bombing. The Swedish Security Service said the arrest was made following collaboration between Scotland and Sweden.
Menni was eventually found guilty of financing terrorism using illegally claimed benefits. He and Abdulwahab had become friends while living in Luton, England.
Anders Thornberg, the Swedish Security (Säpo) chief, told Sveriges Radio that the Stockholm suicide bombing changed Sweden's approach to counter-terrorism.
"Primarily we have much better cooperation now between police authorities and the National Bureau of Investigation (Rikskriminalpolisen)," said Thornberg.
"Having rules about who is responsible for what is not enough. One also has to sit down together and have very, very good plans, to know exactly how things are done, to get to know each other and to practice. Of course we did that before, too, but we have intensified this work, as it is really important," said Thornberg.
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