SALMON farm firms in Scotland are “co-operating” with European investigators in a probe over suspected price-fixing.

The European Commission (EC) inquiry focuses on Norwegian-owned multi-nationals, it has emerged.

Officers moved in on premises operated by three companies in Rosyth, Shetland and Stirling on Tuesday.

The firms involved include Scottish Sea Farms, Grieg Seafood and Mowi, which previously operated under the name Marine Harvest and is the biggest operator in Scotland.

Premises in Netherlands and other EU countries have also been visited, with both Dutch and UK national authorities involved in “unannounced inspections” here.

It is understood that the inquiry centres around alleged price-fixing practices in Norway.

However, because that state is not a member of the European Union, the EC has targeted its action on offices based in nations that do belong to the bloc.

Norwegian producers were responsible for almost 84% of all farmed salmon imported into the EU in 2016.

In a statement, the EC’s competition directorate said it has “concerns that the inspected companies may have violated EU anti-trust rules that prohibit cartels and restrictive business practices” under the Lisbon treaty.

Companies found to have breached these rules can face fines of as much as 10% of their overall turnover.

In a letter given to one company, the EC stated: “The commission has received information, from different actors operating at different levels in the salmon market, alleging that some Norwegian producers of farmed Norwegian Atlantic salmon participate in or have participated [in] different ways of price co-ordination in order to sustain and possibly increase prices of farmed Norwegian Atlantic salmon.”

The EC cautioned: “The fact that the commission carries out such inspections does not mean that the companies are guilty of anti-competitive behaviour nor does it prejudge the outcome of the investigation itself.”.

The names of the companies that were subjected to inspections were not disclosed.

However, Bergen-headquartered Mowi, which has almost 50 salmon farms along Scotland’s west coast, told Reuters that two of its sites in Scotland and the Netherlands had been visited.

Spokesman Ola Helge Hjetland said: “We have nothing to hide, we are co-operating with the European Commission.”

And in a statement, Grieg Seafood, which is majority Norwegian-owned, said: “Grieg Seafood aims to be open, transparent and forthcoming and will provide all necessary information requested by the European Commission DG Competition in its investigation.”

Meanwhile, a spokesperson for Scottish Sea Farms – which is owned by Norway’s Salmar and Leroy Seafood – commented: “We can confirm that we, like other Norwegian-owned companies in Scotland, have been visited by EC officials and are co-operating fully.”

The Scottish Salmon Producers Organisation, which represents the industry, said it understands that “the focus of the investigation is another jurisdiction, not Scotland”.

A spokesperson went on: “The companies concerned are co-operating fully with the investigatory authorities and all further inquiries should be referred to the EC.”

The action follows a major investigation for cartel activity in the US.

Two major players in the American seafood market – StarKist & Co and Bumble Bee Foods – now face multimillion dollar fines after admitting wrongdoing uncovered as the Department of Justice examined an attempted takeover of Bumble Bee by Thai Union Group’s Tri-Union Seafoods.

The $1.5 billion deal fell apart in late 2015 and the would-be buyer, which acted as a whistleblower, will not be subject to a financial penalty.