BRASILIA — Brazil's Agriculture Ministry said on Sunday it has ruled out three potential new cases of Newcastle disease in poultry after testing additional samples taken from animals in the area close to where a first case was confirmed last week.

Newcastle is a viral disease that affects domestic and wild birds, causing respiratory problems, among other symptoms, and can lead to death. Brazil on Thursday detected its first case of Newcastle disease in poultry since 2006.

"The negative results are an extremely positive sign regarding the containment of this sanitary event, which is important for a quick resolution of the situation, and reinforces the robustness of Brazil's agricultural defense system," the ministry said in a statement on Sunday.

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The additional samples were collected on Friday from birds in three properties within the protection zone established in Rio Grande do Sul, where authorities found the first case of the disease in 18 years, when it was detected in subsistence animals.

Last week’s confirmation of the case led the government to enforce a voluntary ban on poultry exports to certain countries.

Brazilian meat lobby ABPA and the state poultry association ASGAV welcomed the results of the additional testing on Sunday, saying they corroborated the single case found last week was “an isolated” event.

Authorities reported the single case on Thursday after the death of around 7,000 birds on a small chicken farm, representing 50 percent of the flock there.

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"I am confident that with the agility of our teams, we will return to normal export operations very soon," Agriculture Minister Carlos Favaro said in Sunday's statement.