Turtle experts said they have identified a fourth specimen of the Yangtze giant softshell turtle (Rafetus swinhoei), one of the world's largest known freshwater turtle species, also one of the world's rarest, in Vietnam's capital city of Hanoi, local media reported on Saturday.

The Hanoi-based Asian Turtle Program of Indo-Myanmar Conservation (ATP/IMC), a Britain-based conservation charity, said they have identified the fourth specimen of the Yangtze giant softshell turtle in Xuan Khanh Lake in Hanoi's outskirts, daily newspaper Vietnam News reported.

ATP/IMC researchers and an ecologist at Washington State University matched environmental DNA collected from water samples from the lake to known samples from the species, and then confirmed the presence of at least one giant turtle living in the lake.

The finding helps to raise the number of these turtles living around the world to four and opens up the opportunity for breeding one of the world's rarest animals.

This finding brings new hope, with the possibility of bringing wild animals together in a controlled environment for captive breeding, daily newspaper Nhan Dan (People) reported. However, the conservation and future of this, the world's rarest turtle species, is far from guaranteed, a great deal of effort is now needed to protect these known animals and ensure they are able to breed, this will mean bringing them together in a single location.

In January 2016, a large male Yangtze giant softshell turtle that had lived in Hanoi's Hoan Kiem Lake died. It was the last surviving individual of the species in the lake and was possibly over 100 years old.

Now believed to be almost extinct in the wild, before the discovery of the fourth specimen in Xuan Khanh Lake, only three specimens were known globally. Two are being kept in Suzhou Zoo in east China, a female and a male that have been together since 2008, but despite successful nesting all of their eggs have been infertile.

Meanwhile, a single wild specimen was found in 2007 by the ATP/IMC that resides in Dong Mo Lake west of Hanoi.

The Yangtze giant softshell turtle, also called the Red River giant softshell turtle, Shanghai softshell turtle or Swinhoe's softshell turtle, was once known from the Red River in Vietnam and from the Yangtze River reaches in China, according to the Turtle Conservation Coalition which has recently released a report on the world's 50 most threatened turtles.