A homemade bomb has been found in the hijacked truck used to kill four people and wound 15 others in Stockholm, according to Sky sources.
Other reports in Sweden say the attacker “burned” himself while trying and failing to detonate the device.
The head of the country’s security agency, Anders Thornberg, would not confirm the find.
Soon after Friday’s attack police released a photo of a suspect and a man who “matches the description” has now been detained over a “terrorist crime”.
The man is reportedly a 39-year-old from Uzbekistan.
Sky sources say he is the attacker and that police were notified by the public of a man who was confused and acting strangely.
He was detained in the suburb of Marsta, not far from the capital’s Arlanda airport.
Eight adults and one child remain in hospital after the attacker hijacked a beer truck and drove it through a crowd and into a department store.
Speaking of the attack, Sweden’s Prime Minister Stefan Lofven said: “These kinds of actions will never succeed. We know that our enemies are these atrocious murderers and not each other.
Source: Sky News