Stockholm department store Ahlens has been forced to apologise after announcing a plan to put "damaged goods" on sale two days after the deadly terror attack that killed four people and wounded 15 others.
The suspected truck driver is a 39-year-old Islamic State sympathizer from Uzbekistan, according to local media reports.
Speaking at a press conference on Saturday, the head of Sweden's National police, Dan Eliason, said security officials had found an object in the truck that "could be a bomb or an incendiary object".
Police Spokesman Lars Bystrom has since told news agencies, "We suspect that the man who was arrested is the perpetrator".
In 2014, the suspect had applied for residency but it was rejected in December a year ago, another police spokesman, Jan Evensson, told reporters.
Jonas Hysing, of Sweden's national police, added that authorities knew he was "sympathetic to extremist organisations, among them IS [the Islamic State group]".
The British man killed in the attack was named as 41-year-old Chris Bevington by the British Government on Sunday night.
According to the Washington Post, Friday's attack marks the "first major apparent terrorist strike in Stockholm".
He reportedly told investigators he was "pleased with what he had done" and had "accomplished what he set out to do", the paper said.
People lay flowers at a memorial ceremony in Stockholm.
Prime Minister Stefan Lofven, who visited a short time later, said: "The goal is that we are supposed to be afraid, but Sweden has shown itself from its best side".
In all, Jan Evenssen of the Stockholm police said authorities have questioned over 500 people in the investigation so far.
The lorry-hijacked from outside a nearby restaurant-crashed into the front of Ahlens department store in the middle of the afternoon on Drottninggatan (Queen Street), one of the city's main pedestrian thoroughfares.