DODOMA, Tanzania (AP) — Authorities in Tanzania say they have seized 368 kilograms (811 pounds) of ivory tusks that conservationists believe were taken from 15 slain elephants.

Tourism Minister Jumanne Maghembe says the tusks are from elephants killed between 2012 and 2014.

A special task force made the seizures at two homes in the Dar es Salaam suburbs of Mbezi beach and Mbagara. Police detained six people including an alleged leader of ivory traffickers.

Poachers have killed tens of thousands of elephants in Tanzania in the past decade.

Friday's announcement comes a day after a U.S.-based conservation group said its South African co-founder had been shot and killed in Tanzania.

The PAMS Foundation said Wayne Lotter was killed Wednesday night in the Masa-ki district of Dar es Salaam.