Veterinarians are monitoring the conditions of two other elephants that saw the ordeal, the Department of National Parks, Wildlife and Plant Conservation said in its latest statement on Sunday.

They are now safe after making their way out of the water on their own, the statement added. Officials had been planning a rescue.

Park officials initially discovered a 3-year-old elephant drowning in the Haew Narok Waterfall, part of the Khao Yai National Park, about 160 kilometres north-east of Bangkok.

Two other elephants had been watching the infant from a cliff. People nearby heard loud cries from the distressed animals in the early hours of Saturday morning, the parks department said.

The young elephant did not survive and officials found five other drowned elephants on the first level of the large three-tiered waterfall, which has been temporarily closed to visitors.