Sabah wildlife director Augustine Tuuga said the department was still tracing the source of the heavy metal and how the animals ingested it.

“If we can find that out, we can find the solution,” Tuuga said today. “The sooner we have the answers, the better.”

Samples analysed by the National Poison Centre found that three of the four elephants found dead over the past month in Sabah’s east coast had high levels of cadmium in their livers and kidneys.

State tourism, culture and environment minister Jafry Ariffin had said yesterday that the matter needed to be investigated urgently as there were no industries in the state producing cadmium or dumping waste containing the material into the environment.

He added that the poison centre also did not find any insecticide or herbicide in the samples it analysed.

The latest elephant found dead was near Sungai Resang, Sukau, in the Lower Kinabatangan wildlife sanctuary, last Saturday.

Police said there were no visible injuries on the elephant and its carcass was intact. A post-mortem later found that the animal had died of inflammation to its internal organs.

Jafry said this was the fourth elephant that had died since the middle of last month in Kunak and Kinabatangan districts.

Experts have estimated that only some 1,500 Borneo pygmy elephants remain in Sabah, with its numbers significantly affected over the years due to human-elephant conflict, including poaching and poisoning.

The recent discovery of cadmium is also the first time wildlife authorities have been able to ascertain the cause of the mysterious deaths of elephants which were found without any visible injury over the years.