The cubs were dug from their icy grave 'complete with all their body parts: fur, ears, soft tissue and even whiskers'. Picture: Vera Salnitskaya

The carcass of one of a pair of extinct big cat cubs will be scrutinised this autumn with the realistic possibility that a liquid found in the remains of the animal is milk from the mother.

Separately, it was recently revealed that samples of the prehistoric infant are being examined by South Korean to clone an animal that once occupied Eurasia from modern day Great Britain to the extreme east of Russia. A source close to the case told The Siberian Times that there is 'hope' the frozen remains of a cave lion cub will show evidence of its mother's milk.

The remains of one of the two cubs is to be preserved intact for years ahead pending further scientific advances. The other will be subjected to an autopsy in Yakutsk, capital of Siberia's Sakha Republic. Pictures: Vera Salnitskaya

Experts do not want to draw premature conclusions but they have 'reason to believe' that the well-preserved innards of two cave lion cubs - one of which will be subjected to an autopsy, the other preserved for future study - contains an opaque white fluid that will prove to be from an extinct lactating lioness.

The preservation of one of the two cubs - which are at least 12,000 years old and possibly much more - allows for its study after new scientific advances. The autopsy on the other will be in Yakutsk, capital of Siberia's Sakha Republic.

The cubs were dug from their icy grave 'complete with all their body parts: fur, ears, soft tissue and even whiskers', said Dr Albert Protopopov, head of the mammoth fauna studies department of the Yakutian Academy of Sciences. The discovery, which received worldwide coverage, was first revealed by The Siberian Times last year.

Laboratory pictures show skin and muscle tissue being extracted from the ancient creature's remains. Pictures: YSIA

Cloning expert Hwang Woo-suk, a South Korean scientist who is already pioneering research work to bring Siberia's extinct woolly mammoths back to life, travelled Yakutsk to obtain samples of one of the cave lion cubs. Laboratory pictures show skin and muscle tissue being extracted from the ancient creature's remains.

Dr Protopopov said: 'Together with the Mammoth Museum, we took samples for cell research.' The museum's experts will study these for the presence of living cells suitable for cloning.

A sudden summer rise - then fall - in the level of the Uyandina River led to cracks appearing and local worker Yakov Androsov spotted an ice lens with the lion cubs inside.

Dr Protopopov said last year when he unveiled the creatures to the media: 'Comparing with modern lion cubs, we think that these two were very small, maybe a week or two old. The eyes were not quite open, they have baby teeth and not all had appeared.'

The cubs were found in Abyisky district, on the bank of the Uyandina River, in 57 kilometres from Belaya Gora village, and presented to the public in November 2015. Pictures: Vera Salnitskaya

He thinks they may have perished after the lioness hid her cubs in a cave to protect them from the hungry lions. 'Then the landslide covered it and they remained surrounded in permafrost. Also the air intake was blocked, and this helped their preservation.' In summer 2016, researchers are due go back to the site and search for remains of possibly one more cub, or even the lioness.

Cave lions - Panthera spelaea (Goldfuss) - lived during Middle and Late Pleistocene times on the Eurasian continent, from the British Isles to Chukotka in the extreme east of Russia, and they also roamed Alaska and northwestern Canada.

Research on the two cubs could help to explain why the species died out around 10,000 years ago, since the animal had few predators, was smaller than herbivores, and was not prone to getting bogged down in swamps, as did woolly mammoths and rhinos. One theory is that a sudden decline in deer and cave bears, their prey, caused the demise of the species.