The world's top exporter of chicken meat was forced to halt exports to its main client China, the European Union and fellow Latin American countries over an outbreak of "highly pathogenic avian influenza" (HPAI) on a farm in the southern state of Rio Grande do Sul.

A case was also later confirmed at Brasilia's zoo, where a pigeon and a duck were found dead, but it did not lead to new restrictions on the poultry industry as it involved wild birds.

On Wednesday, the government said it had informed the World Organisation for Animal Health that the 28-day quarantine period without any new cases being detected had passed.

"The country is declaring itself free of highly pathogenic avian influenza," the agriculture ministry said in a statement.

Agriculture Minister Carlos Favaro announced a "gradual resumption" of poultry exports.

Avian flu has spread globally in recent years, leading to mass culling of poultry, some human deaths, and rising egg prices.

Infections in humans can cause severe disease with a high mortality rate, according to the World Health Organization, but the virus does not appear to move easily from person to person.

Human cases detected so far were mostly in people who had close contact with infected birds and other animals, or contaminated environments.