Dr Wave Kashweeka, Principal Veterinary Officer stands over the carcass of an elephant found near Seronga, in the Okavango Delta, Botswana, July 9, 2020. Botswana wildlife officials investigating hundreds of unexplained elephant deaths have verified six more carcasses and say it is still not clear what is killing the animals, around two months after the first bodies were spotted. REUTERS/Thalefang Charles

Dr Wave Kashweeka, Principal Veterinary Officer stands over the carcass of an elephant found near Seronga, in the Okavango Delta, Botswana, July 9, 2020. Officials told reporters near the Okavango Delta on Thursday that they had now verified 281 carcasses and that the deaths were concentrated in an area of 8,000 square km that is home to about 18,000 elephants. REUTERS/Thalefang Charles

A member of the Botswana Defence Force Anti Poaching Unit stands over the carcass of an elephant found near Seronga, in the Okavango Delta, Botswana, July 9, 2020. Although the number of deaths so far represents a fraction of the estimated 130,000 elephants in Botswana, there are fears more could die if authorities cannot establish the cause soon. REUTERS/Thalefang Charles

A member of the Botswana Defence Force Anti Poaching Unit stands over the carcass of an elephant found near Seronga, in the Okavango Delta, Botswana, July 9, 2020. REUTERS/Thalefang Charles

Dr Wave Kashweeka, Principal Veterinary Officer stands over the carcass of an elephant found near Seronga, in the Okavango Delta, Botswana, July 9, 2020. REUTERS/Thalefang Charles

A herd of elephants walk through the bush near Seronga, in the Okavango Delta, Botswana, July 9, 2020. REUTERS/Thalefang Charles