Brazil's environmental protection agency, Ibama, estimated that approximately 11,000 blue sharks and shortfin mako sharks, which Brazil listed as endangered last month, were killed.

The fins, which were destined for Asia, where shark fin soup is considered a delicacy, were found in two locations.

Almost all of the fins—27.6 tonnes out of the total of 28.7—were seized from a single export company in Brazil's southern Santa Catarina state. Ibama confiscated the remaining 1.1 tonnes at São Paulo's international airport. The agency said it thought it could be the largest seizure by weight of illegally fished shark fins worldwide so far.

Fishing for sharks is illegal in Brazil. Ibama said that the companies were using permits for fishing different species and then illegally targeting sharks.

Ibama's operation targeted two different companies, but others are still under investigation, said the agency's head of environmental protection Jair Schmitt.