Hoan Kiem giant turtle, also known as the rare Rafetus swinhoei, in Dong Mo Lake in Son Tay District, was found dead on April 23 by the lake's keepers, local media reported.

After discovering the turtle's body floating in the water, they immediately invited local authorities to the site to find the cause of death.

The turtle is of the same species as the rare one found in Hoan Kiem Lake in central Hanoi.

It was one of only three of its kind left in the world, with one survivor in Hanoi's Xuan Khanh Lake in Ba Vi District and another in China. With its death, hope for the recovery of the world's rarest turtle species is fading.

The rare Rafetus swinhoei was spotted at Dong Mo Lake in Hanoi in late 2020. Photo: The Asian Turtle Program of Indo-Myanmar Conservation

According to expert Bui Quang Te of the Hanoi Department of Fisheries, the giant turtle in Dong Mo Lake may have died many days before emerging from the water, as was the case with the deceased giant turtle in Hoan Kiem in central Hanoi.

The soft-shell turtle weighs 93 kg and measures nearly 156 cm in length, the expert said, adding that it could be the turtle discovered in Dong Mo Lake in late 2020.

Ta Van Son, director of the Hanoi Department of Fisheries, said a group of researchers discovered the turtle in Dong Mo Lake on October 22, 2020.

"At that time, experts from the Vietnam Academy of Science and Technology and Vietnam National University Hanoi analyzed its DNA and concluded that it belonged to the Rafetus swinhoei species. The scientists weighed, measured, and took samples for genetic testing and released the animal back into the lake," Son added.

This turtle species made international headlines in 2011 when it emerged from the waters of Hoan Kiem Lake after pollution began to take its toll on the creature's health, prompting hundreds of Hanoi residents to roll up their sleeves and organize a cleanup of the lake.

A city conservation plan for the Hoan Kiem turtle for the period 2021-25 aims to identify a suitable environment for breeding the reptiles, and there will be programs for their conservation and reproduction, Son said.

Fisheries expert Bui Quang Te said it is necessary to expand the search area as he strongly believes there could be more turtles living in Dong Mo.

"The Asian Turtle Program of Indo-Myanmar Conservation has carried out several conservation programs in Vietnam's 18 northern provinces since 2003," Te added.

The turtle species, named after Hanoi's Hoan Kiem Lake, where the only turtle of its kind lived, is listed as critically endangered by the International Union for Conservation of Nature and is also on the list of rare and endangered animals requiring urgent conservation efforts under a 2013 decree by the Vietnamese government. The Hoan Kiem Lake turtle died in 2016.

The Dong Mo Lake turtle was first discovered by conservationists from the Asian Turtle Program in 2007. In 2008, during the historic floods in Hanoi, it emerged from the lake and was captured by residents. Thanks to authorities and conservationists, it was returned to the lake and is being monitored to this day.

The creature was first described in 1873, but there has been very little research on this giant soft-shell turtle. The species once inhabited most of the Red River Delta but was hunted to near extinction in the 1970s and 1980s.