Stockholm police on Friday arrested several people after explosives were found in a park in the Swedish capital last week, and said investigations would continue.
The police gave no detail on a potential target or a motive, but said there was still no suspicion of a terror-related crime.
On Sunday, three weeks before a general election in which crime is set to be a major issue among voters, police had destroyed a bag containing explosives in the park, which was among venues for an annual Cultural Festival.
"Since Sunday, we have worked intensely with great resources and all specialist knowledge that we have," Stockholm police said in a statement late on Friday, adding it would give no further comment.
A preliminary investigation has been opened while the dangerous object is examined at the national forensic centre to decide, amongst other things, whether it was functional.
"It is not clear when the analysis will be done," the police said.
(Reporting by Helena Soderpalm; Editing by Sandra Maler)
