The laboratory at the centre of scrutiny over the pandemic has been carrying out research on bats from the cave which scientists believe is the original source of the devastating outbreak.

Documents obtained by The Mail on Sunday show the Wuhan Institute of Virology undertook coronavirus experiments on mammals captured more than 1,000 miles away in Yunnan – funded by a $3.7 million grant from the US government.

Sequencing of the Covid-19 genome has traced it to bats found in Yunnan's caves.

The laboratory at the centre of scrutiny over the coronavirus pandemic has been carrying out research on bats from the cave which scientists believe is the original source of the devastating outbreak 

It comes after this newspaper revealed last week that Ministers here now fear that the pandemic could have been caused by a virus leaking from the institute.

Senior Government sources said that while 'the balance of scientific advice' was still that the deadly virus was first transmitted to humans from a live animal market in Wuhan, an accident at the laboratory in the Chinese city was 'no longer being discounted'.

According to one unverified claim, scientists at the institute could have become infected after being sprayed with blood containing the virus, and then passed it on to the local community.

Now The Mail on Sunday has learned that scientists there experimented on bats as part of a project funded by the US National Institutes of Health, which continues to licence the Wuhan laboratory to receive American money for experiments.

Results of the research were published in November 2017 under the heading: 'Discovery of a rich gene pool of bat SARS-related coronaviruses provides new insights into the origin of SARS coronavirus.'

The exercise was summarised as: 'Bats in a cave in Yunnan, China were captured and sampled for coronaviruses used for lab experiments. 

'Stop blaming us': Letter from the Chinese Embassy  

Last week, The Mail on Sunday carried an article propagating a groundless theory that links the origin of Covid-19 to a lab in Wuhan. 

The article also discredits China’s effective efforts in combating Covid-19 and promoting international co-operation.

There has been no scientific or medical conclusion yet on the origin of Covid-19, as relevant tracing work is still under way. 

The World Health Organisation has made repeated statements that what the world is experiencing now is a global phenomenon, the source is undetermined, the focus should be on containment and any stigmatising language referring to certain places must be avoided.

The name Covid-19 was chosen by the WHO for the purpose of making no connections between the virus and certain places or countries.

The origin of a virus is a complicated, scientific issue. It should be left to scientists and doctors to find out through studies and research. 

Hasty and reckless allegations, such as naming China as the origin in an attempt to shift the blame, before any scientific conclusion is reached, is totally irresponsible and will definitely do harm to international co-operation at this critical time.

China and the UK exchanged views seriously on the origin of the virus and reached consensus. 

In his telephone conversation with Foreign Secretary Dominic Raab, State Councillor and Foreign Minister Wang Yi pointed out that ‘alarmingly, some people are attempting to politicise the epidemic, label the virus and stigmatise China.

‘Such moves are extremely harmful to international co-operation and solidarity, and will only disrupt the joint efforts of various parties to tackle the virus. 

'It is believed that the world, including the UK, will respond in an objective and fair manner and reject such narrow-minded actions’.

Mr Raab expressed the UK’s firm opposition to politicising the outbreak and fully agrees with China that the source of the virus is a scientific issue that requires professional and science-based assessment.

Covid-19 is a global challenge. The right thing to do for every responsible stakeholder, including the media, is to work together and leave no place for rumours or prejudice. 

Chinese Embassy, London 

'All sampling procedures were performed by veterinarians with approval from the Animal Ethics Committee of the Wuhan Institute of Virology.

'Bat samplings were conducted ten times from April 2011 to October 2015 at different seasons in their natural habitat at a single location (cave) in Kunming, Yunnan Province, China. Bats were trapped and faecal swab samples were collected.'

Another study, published in April 2018, was titled 'fatal swine acute diarrhoea syndrome caused by an HKU2-related coronavirus of bat origin' and described the research as such: 'Following a 2016 bat-related coronavirus outbreak on Chinese pig farms, bats were captured in a cave and samples were taken. 

Experimenters grew the virus in a lab and injected it into three-day-old piglets. Intestinal samples from sick piglets were ground up and fed to other piglets as well.'

Senior Ministers say that while the latest intelligence does not dispute the virus was 'zoonotic' – originating in animals – it no longer rules out that the virus first spread to humans after leaking from a Wuhan laboratory.

Last week, further doubt was cast on the animal market theory after Cao Bin, a doctor at the Wuhan Jinyintan Hospital, highlighted research showing that 13 of the first 41 patients diagnosed with the infection had not had any contact with the market. 'It seems clear that the seafood market is not the only origin of the virus,' he said.

The £30 million Wuhan Institute of Virology, the most advanced laboratory of its type on the Chinese mainland, is based ten miles from the now infamous wildlife market.

Last night, Anthony Bellotti, president of the US pressure group White Coat Waste, condemned his government for spending tax dollars in China, adding: 'Animals infected with viruses or otherwise sickened and abused in Chinese labs reportedly may be sold to wet markets for consumption once experiments are done.'

US Congressman Matt Gaetz said: 'I'm disgusted to learn that for years the US government has been funding dangerous and cruel animal experiments at the Wuhan Institute, which may have contributed to the global spread of coronavirus, and research at other labs in China that have virtually no oversight from US authorities.'

A letter from the Chinese Embassy, responding to our report last week about the possible leak from the Wuhan Institute, is published in today's edition.

It says: 'Hasty and reckless allegations, such as naming China as the origin in an attempt to shift the blame before any scientific conclusion, is irresponsible and will definitely do harm to international co-operation at this critical time.

'China and the UK exchanged views seriously on the origin of the virus and reached consensus. 

'In his telephone conversation with Foreign Secretary Dominic Raab, State Councillor and Foreign Minister Wang Yi pointed out that 'alarmingly, some people are attempting to politicise the epidemic, label the virus and stigmatise China...'

'Raab expressed the UK's firm opposition to politicising the Covid-19 outbreak and fully agrees with China that the source of the virus is a scientific issue that requires professional and science-based assessment.'