Thai wildlife officials have discovered the carcasses of five more wild elephants downstream from a waterfall where the bodies of six other elephants were found at the weekend.

National Parks spokesman Sompote Maneerat says the carcasses were discovered by a drone being used to investigate how the first six elephants plunged to their deaths at the Haew Narok – “the Ravine of Hell” – waterfall in Khao Yai National Park in northeastern Thailand.

Park officials say the first group of elephants evidently died when trying to reach a dead calf.

Sompote said on Tuesday the death toll of 11 was the highest number of elephants to die in a single incident in Khao Yai.

The elephant population at the park is estimated to be about 300.