January 28, 2008.

QUITO (AFP) - Ecuadoran authorities are investigating the massacre of 53 sea lions that were found with crushed skulls in the Galapagos Islands, the endangered natural reserve's officials said Monday.

The dead animals were in an advanced stage of decomposition when they were discovered on the island of Pinta, scattered in a one-kilometer (half-mile) radius, said Galapagos National Park official Victor Carrion.

"The sea lions, including 13 pups, died because of a strong blow from someone. It was a massacre whose motives the prosecutor's office must clarify," Carrion told AFP.

The animals' remains did not appear to have been mutilated, and no cuts were found on their skins or limbs, he said.

The authorities found no other killed animals but they stepped up patrols of the islands, Carrion said.

The Galapagos islands are 1,000 kilometers (620 miles) off the coast of Ecuador in the Pacific ocean.

The United Nations Educational, Scientific and Cultural Organization (UNESCO) placed the islands on its list of endangered world heritage sites last year, saying they were threatened by invasive species, growing tourism and immigration.