The mysterious death of hundreds of elephants in Botswana has stumped local authorities and conservationists.
According to Botswana's Environmental Ministry, more than 275 elephants in the northern Okavango Delta have inexplicably died in recent weeks.
Other reports by animal rights activists have cited more than 356 deaths.
Specimens from some of the carcasses have been sent to Canada and the neighbouring countries of South Africa and Zimbabwe for testing, authorities said in a statement.
Last year, an anthrax outbreak killed hundreds of elephants in the same area.
However, anthrax and poisoning have been ruled out by authorities in his instance, as has poaching, as the dead animals were found with their tusks intact.
Hunting ban lifted
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.
The number was "far more than Botswana’s fragile environment, already stressed by drought and other effects of climate change, can safely accommodate," Masisi explained.
Ron Thompson, a conservationist for True Green Alliance, told the Botswana government was correct in reducing the elephant population, as too many elephants destroy the habitat of other species.