A hoard of 500 dead sea lions was mysteriously found recently on a Peruvian beach, leaving scientists puzzled.

Bodies of adults as well as young juveniles were scattered across Anconcillo beach in the Santa Province, Ancash region, located just 400 kilometers (250 miles) north of the capital, Lima, BBC News reports.

Environmental experts told local news agency Andina that they suspect fishermen of poisoning the sea mammals, which usually come close to the shore looking for food. However, Peruvian police are looking into other possible causes of these rotting corpses as well, including disease, entanglement in fishing nets and the accidental ingestion of plastic.

Due to a possible public health hazard, city workers quickly hauled away the bodies and took them to a local dump.

Interestingly, this isn't the first incident of dead sea lions to occur in Peru. According the Agence France-Presse, earlier this month in the Piura region farther north, the bodies of nearly 200 sea lions, along with four dead dolphins, sea turtles and dozens of pelicans, washed ashore.

Officials are still investigating the causes of those mysterious deaths. Given the similarity between these two recent cases, it's possible the same rational can explain them both.

Not to mention, BBC notes, that in 2012 hundreds of dolphins were found dead along a stretch of Peruvian coastline.

While the environmental group named Orca blamed the deaths on the noise and pressure waves caused by ongoing oil exploration in the area, a government report said otherwise.

The Sea Institute of Peru (IMARPE) at the time ruled out oil exploration as a possible explanation, as well as infection by a bacteria or virus for these puzzling fatalities, and instead blamed natural causes.

According to the World Wildlife Fund, sea lions are vulnerable to the effects of climate change on ocean currents, which impacts the number of feed they rely on for food. They are also victims of bycatch in fisheries and subject to diseases spread by other species, such as dogs.

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