The extortion letters mailed to unique recipients have stamps and postmarks.

But despite the police calling for a report, a woman in Stockholm and her family were informed that the preliminary investigation was closed immediately.

- A police officer at Säpo whom we contacted said that there are probably professional criminals behind it - but that we probably didn't need to be worried, she says.

The blackmail letters are spread across the country

Since the woman and her family received the letter, more threatening letters have rattled in across the country, and the police are now putting together a big puzzle.

- It's about a lot of letters - and it's completely ordinary people who receive them, says police spokesperson Daniel Wikdahl.

Footnote: Hear her read the letter in the video.