Buenos Aires, Argentina - A sei whale stranded on a sandbank in Argentina's Río de la Plata river has died despite a large-scale rescue operation, the Temaikén conservation foundation said on Saturday.
"Unfortunately, despite every effort, the animal did not survive," the foundation said.
Rescue teams spent more than a day trying to free the whale, which local media reported was about 7 meters (23 feet) long, after it became stranded off the coast of San Fernando, a suburb north of Buenos Aires.
The whale's condition had been described as critical from the outset, with its full body weight resting on its abdomen and affecting the function of its internal organs. Rescuers kept the animal's skin wet to reduce stress.
The rescue teams had hoped to use the rising tide to refloat the whale and guide it into deeper water so it could return to the sea. However, the attempt was unsuccessful.
Large tidal fluctuations and numerous sandbanks are common in that part of the Río de la Plata.
The whale was first spotted on Friday. During the Southern Hemisphere winter, sei whales migrate north along Argentina's Atlantic coast.
The foundation said it was likely the whale had become disoriented due to a combination of environmental factors or a health problem, swum upstream, and eventually become stranded on the sandbank.