The crimes must have been committed in connection with the Ica traders' union and the pension giant AMF buying out Ica from the Stockholm Stock Exchange.
The union and AMF placed a buyout bid of SEK 534 per share in November last year.
The share was delisted in January.
In the weeks before the bid, the share rushed on the stock exchange.
Jonas Myrdal, chamber prosecutor at the Swedish Environmental Crime Agency (EBM), states that it is obvious that inside information has been leaked about the bid.
Attack on the head office
Earlier this week, EBM and the police raided the traders' union's headquarters in Solna.
Göran Blomberg, CEO of the Ica traders' union, said at the time that he had not received any indications that there had been any leaks and stated that the suspicions did not affect anyone at the union.
A total of 13 people have been arrested on suspicion of involvement in the crime.
On Thursday afternoon, three of them were arrested.
Two of the three are sole owners of larger Ica stores with annual sales of SEK 200–250 million and annual share dividends of several million kronor.
The third is store manager for a major Ica retailer in southern Sweden.
On the same day, the Ica Traders' Association published a press release stating that they "take the situation very seriously".
Investigation continues
During Friday, four more suspects were arrested.
The other six, of the thirteen, have been released but the criminal suspicions against them remain.
The suspects in the case are residents of southern and central Sweden.
- What is happening now is that we are holding a large number of interrogations and analyzing seizures made in connection with the raid earlier this week.
It can be about telephones, computers and other material that we go through, says chamber prosecutor Jonas Myrdal in a press release.