Botswana reports mysterious deaths of hundreds of elephants
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.
Chris Foggin, from Zimbabwe's Victoria Falls Wildlife Trust, which conducted the tests on elephant samples from Botswana, said only that country's government could share the findings.
The Botswana wildlife department has said the government contacted neighbours Zimbabwe, Angola, Namibia and Zambia but they had not seen similar elephant deaths.
Africa's overall elephant population is declining due to poaching, but Botswana, home to almost a third of the continent's elephants, has seen numbers grow from 80 000 in the late 1990s.