Last month, officials with the Kenya Wildlife Service attempted to move 11 endangered black rhinos from two national parks, Nairobi and Lake Nakuru, to a third, Tsavo East. Nine of them died shortly after arriving in their new home from what an autopsy has shown to be salt poisoning.

Today, the Kenyan government announced that a tenth rhino has died and that the eleventh — now the sole survivor of the translocation operation — was attacked by lions yesterday and is clinging to life.

The black rhinoceros is a Critically Endangered species, according to the IUCN Red List. Only about 5,500 individuals are believed to survive in the wild today, 750 of them in Kenya.

Last month, officials with the Kenya Wildlife Service attempted to move 11 endangered black rhinos from two national parks, Nairobi and Lake Nakuru, to a third, Tsavo East. Nine of them died shortly after arriving in their new home from what an autopsy has shown to be salt poisoning and dehydration.

Today, the Kenyan government announced that a tenth rhino has died and that the eleventh — now the sole survivor of the translocation operation — was attacked by lions yesterday and is clinging to life.

According to a report from eNews Channel Africa, Kenyan Tourism Minister Najib Balala said at a press briefing in Nairobi this morning that an investigation had determined that “negligence” by the transfer team had led to the 10 rhinos’ deaths due to “multiple stress syndrome intensified by salt poisoning.”

The rhinos were taken to Tsavo East National Park in southern Kenya, one of the country’s oldest and largest parks, in order to establish a new breeding ground for the animals in the hopes that they would start a new population. The black rhinoceros is a Critically Endangered species, according to the IUCN Red List. Only about 5,500 individuals are believed to survive in the wild today, 750 of them in Kenya.

Autopsies found the water at the endangered black rhinos’ new home in Tsavo East had such a high concentration of salt that it was harmful to the animals, Balala said at the press conference. The BBC reports that Balala added that the Kenyan government had sampled the water in Tsavo East before relocating the rhinos there, but failed to take the results of those tests into consideration. The rhinos ultimately died of dehydration, upper respiratory tract bacteria, and gastric ulcers.

Balala also announced that the eleventh relocated rhino was in critical condition after the lion attack. The rhino “was treated and so far we are monitoring that eleventh rhino,” he said.

Several Kenya Wildlife Service officials who were involved in the relocation operation have reportedly been suspended.

The Kenyan arm of the WWF runs the rhino translocation program with the Kenya Wildlife Service. Though WWF Kenya CEO Mohamed Awer described the translocation process as “extremely challenging” in a statement to CNN, he said the risk was worth it given the odds stacked against the species.

“At a time when three rhinos are poached on average a day for their horns, any losses are particularly painful,” Awer told CNN. “Translocating wild animals of this size is extremely challenging and not without risk, but black rhinos are under enormous threat so efforts to try and better protect them, such as translocations, are crucial for future generations.”

Kenya’s Tourism and Wildlife Ministry said that nearly 150 black rhinos were translocated to new habitats in the country between 2005 and 2017, and just eight died after being transferred.

Poaching driven by the demand for rhino horn for use in traditional medicinal practices in China and Vietnam is the chief threat facing the world’s remaining black rhinos. There are no scientifically proven medical benefits associated with rhino horn, which is made of keratin, the same substance as human hair and fingernails.