The mystery surrounding hundreds of sudden elephant deaths in Botswana seems to have been solved.
More than 350 elephants were reported to have died in Botswana in recent weeks but the cause of death had remained unknown.
Now, the country has pointed to a naturally occurring toxin as a probable cause, according to a senior wildlife official.
Botswanan officials launched an investigation after Elephants Without Borders (EWB), a conservation organisation, reported that its own aerial surveys showed elephants of all ages appeared to be dying.
The group counted 169 dead elephants on May 25, and another 187 on June 14. The Botswana Department of Wildlife and National Parks confirmed 281 elephants had died.
"Several live elephants that we observed appeared to be weak, lethargic and emaciated," EWB director Mike Chase said at the time.
"Some elephants appeared disorientated, had difficulty walking, showed signs of partial paralysis or a limp. One elephant was observed walking in circles, unable to change direction although being encouraged by other herd members."
Mr Chase also said urgent action was needed to establish if the deaths were caused by disease or poisoning.
Authorities had been struggling to establish the cause of death more than two months after carcasses were spotted in the Okavango Panhandle region earlier this year.
Conservationists feared the deaths could spiral out of control if a cause could not be established quickly.
Officials have ruled out poaching as the cause of death, because the elephant carcasses were found intact.
It was highly unlikely that an infectious disease was behind the deaths of at least 281 elephants, said Cyril Taolo, acting director of the Botswana Department of Wildlife and National Parks.
Mr Taolo said the investigation was concentrating on toxins produced naturally from bacteria, possibly in sources of water.
On July 3, the Ministry of Environment, Natural Resources, Conservation and Tourism said in a statement that, "three laboratories in Zimbabwe, South Africa and Canada have been identified to process the samples taken from the dead elephants".
This week, principal veterinary officer of the Department of Wildlife and National Parks, Mmadi Reuben said: "So far 275 carcasses have been verified of the 356 reported.
"The team has collected a number of biological samples from the fresh carcasses and also some environmental samples which have been sent to different labs for further analysis. And in the meantime the team continue to monitor the situation, recover ivory from the carcasses and safely dispose of elephant carcasses that are nearer to human settlement and villages." - ABC/Agencies