"Yes, it is correct, it is likely him," police spokesman Lars Bystrom told The Associated Press. He declined to comment on Swedish media reports that the suspect was a 39-year-old man from Uzbekistan.
There was no immediate claim of responsibility for yesterday's attack.
Earlier, prosecutor Hans Ihrman said a person had been formally identified as a suspect "of terrorist offenses by murder," and should face a pre-trial custody hearing before midday Tuesday or be released.
Stockholm's Karolinska hospital said six of those injured in the attack had been released and eight adults and one child were still in the hospital.
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Government offices were flying flags at half-staff to honor the victims.
Sweden's vice-prime minister, Isabella Lovin, and Education Minister Gustav Fridolin laid red and yellow roses today morning, close to the site of the attack.
The stolen beer truck traveled for more than 500 yards (meters) along a main pedestrian street known as the Drottninggatan before it smashed into a crowd outside the upscale Ahlens department store about 3 pm yesterday.
"People were screaming and running in all directions," said Brandon Sekitto, who was in his car nearby. "(The truck) drove straight into the Ahlens entrance."
"I saw the driver, a man in black who was light around the face," Brandon told Swedish daily Dagens Nyheter. "Some women were screaming, 'Run! Run!'"
Prime Minister Stefan Lofven said yesterday that the attack "indicates that it is an act of terror."
Later last night, Lofven laid a bouquet of red roses and lit a candle near the site.