NAIROBI, Kenya -- Eight critically endangered black rhinos are dead in Kenya following an attempt to move them from the capital to a national park hundreds of kilometers away, the government said Friday, calling the toll "unprecedented" in more than a decade of such transfers. Preliminary investigations point to salt poisoning as the rhinos tried to adapt to saltier water in their new home, the Ministry of Tourism and Wildlife said in a statement. It suspended the ongoing move of other rhinos and said the surviving ones were being closely monitored.

Prominent Kenyan conservationist Paula Kahumbu of WildlifeDirect called the loss of the rhinos "a complete disaster."

In moving the rhinos to Tsavo East National Park last month, the Kenya Wildlife Service said it hoped to boost the population there.

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In moving a group of 11 rhinos to the newly created Tsavo East National Park from Nairobi last month, the Kenya Wildlife Service said it hoped to boost the population there. The government agency, which has conducted numerous successful moves in the past, has not said how the rhinos died. Fourteen of the animals were to be moved in all.

"Disciplinary action will definitely be taken" if the findings of an investigation indicate negligence by agency staff, Kenya's wildlife ministry said.

Kenya is home to 80 percent of the black rhinos' remaining global population, Kahumbu said.

"Moving rhinos is complicated, akin to moving gold bullion, it requires extremely careful planning and security due to the value of these rare animals," she said in a statement. "Rhino translocations also have major welfare considerations and I dread to think of the suffering that these poor animals endured before they died. We need to know what went wrong so that it never happens again."

Transporting wildlife is a strategy used by conservationists to help build up, or even bring back, animal populations. In May, six black rhinos were moved from South Africa to Chad, restoring the species to the country in north-central Africa nearly half a century after it was wiped out there.

Kenya transported 149 rhinos between 2005 and 2017 with eight deaths, the wildlife ministry said.

According to WWF, black rhino populations declined dramatically in the 20th century, mostly at the hands of European hunters and settlers. Between 1960 and 1995 numbers dropped by 98 percent, to fewer than 2,500.

Since then the species has rebounded, although it remains extremely threatened. In addition to poaching the animals also face habitat loss.

African Parks, a Johannesburg-based conservation group, said earlier this year that there are fewer than 25,000 rhinos in the African wild, of which about 20 percent are black rhinos and the rest white rhinos.

In another major setback for conservation, the last remaining male northern white rhino on the planet died in March in Kenya, leaving conservationists struggling to save that sub-species using in vitro fertilization.