More than 400 dolphins were found dead on the Pacific Ocean beaches in the past few weeks, the Associated Press reported.

The Peruvian Sea Institute, or Imarpe, is investigating the cause of death. They will also try to figure out why the sea creatures beached themselves in the northern regions of Lambayeque and Piura, El Comercio reported.

Technician Jaime de la Cruz of Peru's IMARPE marine life agency told the AP about 220 dead dolphins were found in the last week of January. The rest were discovered during the previous three weeks.

Tests conducted on tissue samples of the marine mammals showed that the dolphins were not poisoned by fishermen and did not "die from the effects of extractive activities in the regions," The Australian reported.

Cruz told El Comercio the dolphins may have died from ingesting toxic algae.

Similar beachings of dolphins occurred in the past two years in central and northern Peru.

According to the AP, More than 800 beached dolphins were encountered on the Pacific Ocean beaches in 2012. Authorities never established the cause of death of the dolphins found in 2012.

However, the Australian, citing an Imarpe report, said the dolphins found in 2012 died from natural causes. Authorities ruled out contact with fishing vessels, pesticides, pollution from heavy metals and seismic mining exploration were among the human causes ruled out.

The report also ruled out lack of food, bacterial infections, viral infections and biotoxins, some possible natural causes of the deaths, according to The Australian.

Autopsy results are expected in two weeks, the AP reported. The exam will focus on lungs, kidneys and livers.