Kazakh authorities say some 100 saiga antelope have been found dead in a northern region, with few clues as to what killed the critically endangered animals.
The Kazakh Agriculture Ministry says local forest inspectors found the animals' remains in the Amangeldy district of the Qostanai region on May 11.
It is the latest mass die-off to strike the increasingly rare ungulates in the Eurasian steppe region.
In May 2012, nearly 1,000 dead saiga antelope were found, also in Qostanai. Environmental activists blamed those deaths on the landing in the region of a Russian spacecraft carrying a Russian-American crew from the International Space Station less than a month earlier.
That connection has never been proven, and the Agriculture Ministry later said the deaths were the result of an infection carried in the mouth and breathing passage called pasteurellosis.
In 2012 and then 2014, Kazakh officials said dozens of saiga antelope were found shot dead with their horns removed in the northwestern region of Aqtobe and the northern region of Aqmola, adding that saiga horns are used in traditional Tibetan and Chinese medicine.
No one has been prosecuted for the shootings.
Some Kazakh activists continue to insist Russia's space program is at fault and have demanded that the government end launches at the Soviet-built Baikonur Cosmodrome, in central Kazakhstan, of Russia's Proton-M carrier rockets.
Several Proton-M rockets, which use highly toxic fuel, have exploded over Kazakh territory after launch from Baikonur.
The accidents created toxic clouds that angered local residents and environmental activists.
The saiga is a critically endangered species, with most of the surviving animals in Kazakhstan, parts of Mongolia, and Russia's Kalmykia Republic.
Some estimates say only around 50,000 saigas survived years of unrestricted hunting following the Soviet collapse.