European Union antitrust officials raided fisheries in multiple countries on Tuesday, investigating a possible farmed Atlantic salmon cartel.

The EU Commission confirmed Tuesday that raids were carried out but did not name the targeted companies — although a number of Norwegian firms have confirmed their involvement.

“Unannounced inspections are a preliminary investigatory step into suspected anti-competitive practices,” the EU said in a statement. “The fact that the Commission carries out such inspections does not mean that the companies are guilty of anti-competitive behavior nor does it prejudge the outcome of the investigation itself.”

Mowi, the world’s biggest producer of farmed Atlantic salmon, confirmed to Reuters that it was one of the inspected companies. “We have nothing to hide; we are cooperating with the European Commission,” spokesman Ola Helge Hjetland said. Known as Marine Harvest until Jan. 1, the firm supplies one-fifth of the world’s farmed Atlantic salmon and reported a record €3.8 billion ($4.3 billion) in revenue for 2018.

Grieg Seafood of Norway also confirmed that one of its facilities in Scotland’s Shetland Islands had been inspected. “We have been informed that The European Commission DG (Director General) Competition is exploring potential anti-competitive behavior in the salmon industry. They have performed an inspection today at Grieg Seafood Shetland,” a spokesperson told SeafoodSource. “The salmon market is very competitive and we are not aware of any anti-competitive behavior. We are co-operating with the European Commission DG Competition’s investigation.”

At the same time, Norway’s SalMar said officials had raided Scottish Sea Farms, its joint venture with Lerøy Seafood, which hasn’t been having a great year: Lerøy lost 2.6 million salmon hatchlings in a fire at a Norwegian facility in January.

The competition authority of Norway, which is not an EU member, was not involved in the Commission’s investigation, a spokesperson told Reuters. There’s also no deadline for the EU investigation.

Companies in violation of EU antitrust rules can be fined up to 10% of their global revenue. Undercurrent News reports that could be as much as €850 million, however, sources were unsure if the focus of the investigation is on sales from farmers to processors, or from processors to retailers — or both.