Thieves broke into a pop-up package pick-up centre in Tampere operated by national mail company Posti, and stole 156 packages on Sunday night, according to the firm.
This type of situation is rare, but not unheard of, according to Posti's chief of security, Heikki Horn.
The exact number of the missing packages is known because all of the parcels were labelled and registered in Posti's database, Horn explained.
"They did not take all of the packages, some were left behind. For customers [the thefts are] very sad, of course," he said.
The temporary package pick-up centre in question is located on Vestonkulma in the Leinola district and, like similar temporary pick-up centres, is open daily during the busy run-up to the holidays.
Employees coming into work on Monday morning were the first to notice the break-in and then notified police, who are now investigating the case.
Posti is now focusing on reaching out to the stolen packages' recipients and senders, the firm's security chief Horn said.
Some of the parcels had been ordered online while others were sent by private individuals, according to Posti.
However, the postal company has not yet considered making specific changes to security routines because of the incident.
"We have not yet drawn those kinds of long-term conclusions about this, because the police investigation is still in progress," Horn said.
Posti has set up 33 similar pop-up package facilities across the country during the Christmas season.
Posti delivered around 7.4 million packages in the run-up to Christmas last year, according to the company.
The story was first reported by local newspaper Aamulehti.