Dead bottlenose dolphins have washed up in their hundreds on Peru’s beaches (VIDEO)

Hundreds of dead bottlenose dolphins have washed ashore on Peru's northern coast over the past three days, leaving officials struggling for answers as to what killed the marine animals.

At least 264 dead dolphins were found over a 70-mile stretch of sandy beach, Agence France-Presse reported, citing Edward Barriga, an official with Peru's Oceanic Institute (IMARPE).

"We have taken samples to determine the cause of death," Barriga reportedly said from Lambayeque.

Vast quantities of dead anchovies had also been found in the region, located nearly 500 miles north of Lima, the Peruvian capital.

The head of a group representing Lambayeque aquafarmers, Jorge Cabrejos, said the anchovies appear to have eaten contaminated plankton, which then sickened the dolphins that ate the small fish.

However, the authorities have not yet ruled out the possibility of hunting killings, the BBC reported.

Local residents quickly carved up some of the mammals for meat, ITN reported.

Meanwhile, Carlos Yaipen of ORCA, a non-governmental group that focuses helping ocean creatures in the south Pacific, suggested the dolphins may have been killed by the impact of off-shore oil exploration and drilling in the region.

According to AFP:

"Thirty-four of the world's 81 species of cetaceans swim off the Peruvian shores, 17 of which are dolphins. Of those, the most common is the bottlenose dolphin."