Sharks positive for… cocaine were detected in off the coast of Brazil, according to scientists.

Marine biologists tested 13 Brazilian tipper sharks taken off the coast near Rio de Janeiro and, according to the BBC, high levels of cocaine were found in their muscles and liver.

Concentrations were up to 100 times higher than previously reported for other aquatic creatures.

The research, carried out by the Oswaldo Cruz Foundation, is the first to detect the presence of cocaine in sharks.

Experts believe that cocaine enters the waters through illegal laboratories where the drug is made or through the feces of drug users.

Packages of cocaine lost or thrown overboard by traffickers could also be a source, although this is less likely, researchers say.

Sara Novais, a marine ecotoxicologist at the Center for Marine and Environmental Sciences of the Polytechnic University of Leiria, told Science magazine that the findings are “very important and potentially alarming’.

All the females were pregnant, but the effects of cocaine exposure on fetuses are unknown, experts say. Further research is needed to determine whether cocaine changes the behavior of sharks.

However, previous research has shown that drugs are likely to have similar effects in animals as they do in humans.

Last year, chemicals including benzoylecgonine, which is produced by the liver after cocaine use, were found in seawater samples collected off the south coast of England.