Postal workers in a Brazilian border town knew there was something suspicious about the shipments from Argentina but were stunned to find scorpions and poisonous snakes in the express mail.
The contraband animals, which also included iguanas, tortoises and lizards, were discovered when the workers had the boxes X-rayed.
A spokesman for the federal police in Foz do Iguacu, the town on the border with Argentina and Paraguay where the incident occurred, said animals shipped into the country often end up in Europe "where they charge three, four, five times as much."
Television stations broadcast images of brightly colored tropical snakes coiled and stuffed into plastic containers, the kind typically used for takeaway orders at the deli counter.
The contraband animals had crossed the border from Argentina and were being express-mailed to Brazilian cities, police officer Emerson Rodrigues told TV Globo.
Animals are trafficked in from several countries and often cross into Brazil from Argentina or Paraguay in the triborder region near Foz do Iguacu, authorities said.
"Traffic also goes the other way, which is to say the animals come from Brazil and go to other countries, including to Europe," Rodrigues told Globo.
Police suspected the express mail case was linked to an international trafficking ring and were using the addresses on the boxes as leads.
Animal trafficking is common in South America, where the Amazon rain forest alone is estimated to hold some 15 percent of all plant and animal species on earth.
Foz do Iguacu is south of the Amazon at the edge of the Pantanal wetlands, which are famous for giant otters, alligators and various birds including storks and South America's endangered blue Hyacinth Macaw.
In Brazil, macaws and other parrots are among the most commonly trafficked animals. They are often found dead or dying in boxes and crates when trafficking rings are broken up.