Jan 25 (Reuters) - The European Commission has informed six Norwegian salmon producers of its suspicion that they breached EU antitrust rules by distorting competition for spot sales of Norwegian farmed Atlantic salmon in the EU, it said on Thursday.

The Commission said it was concerned that Cermaq, Grieg Seafood, Bremnes, Leroy, Mowi and SalMar had exchanged commercially sensitive information about prices and volumes between 2011 and 2019 to reduce market uncertainty.

Mowi, SalMar, Leroy and Grieg Seafood issued statements contesting the Commission's preliminary findings, maintaining their commitment to competition laws and expressing their intention to cooperate with the investigation.

Cermaq said it explicitly disagreed with the Commission's preliminary findings but will refrain from further comment until watchdog's final decision.

A Bremnes representative was not immediately available for comment.

Shares in Mowi, SalMar, Leroy and Grieg Seafood fell 4.9%, 1.9%, 5.7% and 7.1% respectively after the Commission announcement.

Antitrust regulators raided salmon farms in several European Union countries in February 2019, including some owned by Mowi, on suspicions of involvement in a cartel.

The Commission did not name the companies at the time. But Mowi, the world's biggest producer of farmed Atlantic salmon, said that EU regulators had raided two of its businesses, in Scotland and the Netherlands.

Norway accounts for more than half of the farmed Atlantic salmon worldwide and the EU is its main importer.

The alleged conduct concerns sales of fresh, whole and gutted Atlantic salmon farmed in Norway. It does not concern frozen farmed Atlantic salmon or processed products such as salmon fillets, loins or smoked salmon, the commission said.

The statement of objections sent to the companies does not prejudge the outcome of an investigation, it added.

(Reporting by Bart Meijer additional reporting by Jesus Calero Editing by David Goodman )