“They got in there to drink water and could not get out,” Keo Sopheak, the head of the environmental office in eastern Mondulkiri province, said.

He said the threemetredeep mud pit, created by a bomb during the country’s civil war, was located in a protected forest area and had been enlarged by local villagers to store water.

The elephants were discovered in the crater on Friday, said Keo Sopheak, with only their rounded backs and heads poking out of the mud pool.

“We had to dig away the edge of the crater by hand to make a path,” the official said, adding that rescuers also pumped water into the crater to thin out the sludge and help the animals climb out.

The elephants lumbered back into the jungle after their rescue.

“They could have died if they had not been spotted,” added Keo Sopheak.

There are believed to only several hundred of the endangered Asian elephants in Cambodia, according to conservation groups.

Like other Asian elephant populations in the region, their livelihood has been increasingly threatened by rapid deforestation and poaching.

Earlier this week a male elephant died after leaning against an electricity pole and causing it to fall down in jungle near Cambodia’s Cardamom Mountains.