WARNING: GRAPHIC CONTENT

Botswana is investigating the mysterious deaths of hundreds of elephants.

The first carcass was found on May 11 by researchers in a helicopter who were trying to find out why an elephant with a satellite tracker hadn’t moved for some time.

They found it dead, along with several others, at a water hole.

Since then, the number of unexplained deaths of elephants has risen to 275 by an official government count. Conservation authorities put it even higher.

Poaching has been ruled out as the carcasses were found intact.

A dead elephant in the Mababe area of Botswana. Photo: AAP

“Three laboratories in Zimbabwe, South Africa and Canada have been identified to process the samples taken from the dead elephants,” Botswana’s Ministry of Environment, Natural Resources, Conservation and Tourism said.

Elephants Without Borders, a conservation organisation, reported that its own aerial surveys showed that elephants of all ages appeared to be dying.

The group counted 169 dead elephants on May 25 and another 187 on June 14.

“Several live elephants that we observed appeared to be weak, lethargic and emaciated. Some elephants appeared disorientated, had difficulty walking, showed signs of partial paralysis or a limp,” EWB director Mike Chase said in a report seen by Reuters.

“One elephant was observed walking in circles, unable to change direction although being encouraged by other herd members.”

In the report, EWB put the death toll at 356. Mr Chase said urgent action was needed to establish if they were caused by disease or poisoning.

Africa’s overall elephant population is declining due to poaching. In Botswana – home to almost a third of the continent’s elephants – elephant numbers have grown from 80,000 in the late 1990s to 130,000.

However, elephants are seen as a nuisance by some farmers, whose crops have been destroyed.

-with AAP