More than 100 hippos have been found dead in a Namibian national park, with authorities suspecting anthrax could be to blame.
The animals are believed to have all died in the last week in the remote Bwabwata National Park, in the country's north-east.
One ministry official said Namibia had never seen anything like this before.
Anthrax is a deadly bacterial disease which is known to kill game, cattle, and sometimes humans.
Pictures from the area show dozens of dead hippos - some on their backs - lying in rivers with low water levels.
Colgar Sikopo, director of parks and wildlife management at Namibia's Ministry for the Environment and Tourism, told
previous outbreaks in Namibia had only killed a couple of hippos and elephants.
"This is a situation that we have seen before," he said, explaining outbreaks like this "mainly occurs when the level of the river is so low".
Namibia's environment minister Pohamba Shifeta told news agency AFP that the country's veterinary services were working on establishing the exact cause. He warned that the exact death toll could be higher due to the possibility that crocodiles may have eaten some of the carcasses.
Anthrax is caused by Bacillus anthracis and can be deadly - but usually it does not spread easily.
It largely survives as spores that hide away in soil for years before entering an animal through a cut or wound.