(CNN) Almost 90 elephant carcasses have been found during a survey in northern Botswana, revealing "unprecedented" levels of poaching in the country, the conservation group carrying out the study has said.

Just nine carcasses were discovered in total during the last audit of the region in 2014, and Elephants Without Borders is expecting this year's number to rise further because the organization is only halfway through the study, which began on July 5 and is largely funded by Botswana's Department of Wildlife and National Parks.

"While we had elephant poaching in the country before this year, it certainly wasn't of the magnitude that we're seeing now. It's completely unprecedented," Mike Chase, director and founder of Elephants Without Borders, told CNN.

"We were always warned that the poaching that has happened in East Africa and parts of northern Mozambique may spread south. What I'm astounded by is the scale and the speed at which it has happened."

Thato Raphaka, Botswana permanent secretary of land management, water and sanitation services, said that 90 elephants were never killed in one incident, and that a recent survey conducted by Elephants Without Borders found 53 carcasses that had already been reported to the government.

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