The fire at the Sokos department store in central Helsinki last Friday was caused by a malfunctioning technical device, according to police.
The item was located in the staff area, officers added.
"The police do not suspect foul play, but the investigation into the cause of the fire is continuing," Detective Inspector Juhani Vuorisalo of the Helsinki Police Department told Yle.
A spokesperson for the S-Group chain, which owns the Sokos store, said that the fire was confined to the first floor and did not result in any injuries.
The store underwent smoke extraction and ionisation detection on Monday to ensure that it was safe to shop and work in the building, and reopened on Tuesday morning.
The S-Market grocery store and Hesburger fast food outlet located in the same building suffered only minor damage, and they both reopened to customers on Saturday.
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