I know nothing about Swedish law, but in the US, there can be both civil and criminal fraud. They might be planning to file a lawsuit also.

Fraud is usually a crime and therefore a matter for the police, even in the US.

It's not going to be a lawsuit. You don't sue companies for breaking the law in Sweden. It's going to be a criminal case if police deem so.

I'm pretty sure the publishers are alleging that a crime has been committed. In that case, private parties can't open a suit (at least if Swedish criminal law is at all similar to Norwegian law), so this asks the police to open a criminal investigation into the matter. What happens next in the Norwegian system at least is that the police will conduct their investigation, and at some point when the police consider their investigations complete the prosecutor's office will decide what to do next. Next steps can be concluding that no crime has occured, to ask the police to investigate further, that a crime has been committed but the evidence are insufficient for a trial, or that someone should be tried.