The staff at the social services department in Växjö raised the alarm after several employees experienced symptoms.
The police set up roadblocks and the national bomb squad was called in. According to the bomb squad's initial assessment, the contents of the letter are harmless.
The investigation is continuing to determine what the contents were. A report of spreading infection, assault and causing danger to others is being filed, the police write on their website.
The people who were near the shipment exhibited allergy-like symptoms, according to Växjö Municipality.
Six people were examined by the medical services. According to the initial assessment, they had minor injuries, Region Kronoberg writes.
