SÃO PAULO, Brazil — A virus that has killed millions of salmon in Chile and ravaged the fish farming industry there was probably brought over from Norway, a major salmon producer has acknowledged.

Cermaq, a state-controlled Norwegian aquaculture company that has become one of the principal exporters of salmon from Chile, has endorsed a scientific study concluding that salmon eggs shipped from Norway to Chile are the “likely reason” for the outbreak of the virus in 2007, according to Lise Bergan, a company spokeswoman.

But, she argued, “the report didn’t pinpoint any company” as the culprit.

The virus, infectious salmon anaemia, or I.S.A., was first reported at a Chilean salmon farm owned by Marine Harvest, another Norwegian company. It quickly spread through southern Chile, wracking a fishing business that had become one of the country’s biggest exporters during the past 15 years. The Chilean industry, whose major clients include the United States and Brazil, suffered more than $2 billion in losses, saw its production of Atlantic salmon fall by half and had to lay off 26,000 workers.

The outbreak in Chile also revealed structural problems within the industry, including overcrowding in pens that environmentalists say probably helped speed the spread of the virus. Since then, the industry and the Chilean government have instituted a wide range of reforms to try to contain outbreaks, but despite extensive efforts to rein it in the virus continues to spread.