Botswana is investigating yet again the mysterious deaths of elephants, only a few months after 330 of the gray giants died from water-borne bacteria, a local wildlife official said Tuesday.

“So far we have been notified of five carcasses that were discovered by researchers from [international conservation organization] Rhinos Without Borders,” Dimakatso Ntshebe, a regional wildlife officer in Botswana’s famous Okavango Delta, told dpa.

Poaching had been ruled out as a possible cause of death as the tusks of all carcasses found in the Moremi Game Reserve on January 24 were intact, according to Ntshebe.

Investigations into the deaths were still at their initial stages, with conservationists expecting to find more carcasses in the difficult to access area, the wildlife officer said.

Preliminary findings however indicated that the five dead elephants showed similar symptoms to the 330 pachyderms killed by water-borne bacteria last year near the Okavango Panhandle, more than 200 kilometres farther north-east.

Last September, the Department of Wildlife and National Parks found after a long investigation that cyanobacteria, which live in the water in the Okavango Delta and can produce deadly toxins, were the reason for the deaths.

Botswana is known for its nature and is a popular tourist destination because of its wildlife. The lifting of a ban on elephant hunting last year caused international outrage.

President Mokgweetsi Masisi said at the time that hunting was necessary to keep the elephant population of close to 130,000 in check.