The US claimed on Saturday that staff at a Chinese virology laboratory became sick with a Covid-like illness in autumn 2019, months before the coronavirus spread widely from Wuhan.

In a long-awaited document from the state department, the Trump administration called for an investigation as it published dubious accusations that a possible "laboratory accident" at the Wuhan Institute of Virology (WIV) may be the source of the global pandemic.

The claims were dismissed by analysts who insist the disease came from a naturally occurring event.

In a statement late on Friday claiming to reveal "undisclosed information", the state department said it "has reason to believe that several researchers inside the WIV became sick in autumn 2019, before the first identified case, with symptoms consistent with both Covid-19 and common seasonal illnesses."

The statement also said that the lab had been carrying out research on a bat coronavirus similar to the Sars-CoV-2 strain that spread globally and that the lab had collaborated with China's military on publications and secret projects.

Some experts were nonplussed by the announcement. "Zero details given," noted Kristian Andersen, an immunologist at Scripps Research, rating the statement as "an F". The fact that Wuhan was home to the world's leading coronavirus research facility before it became known as ground zero for the pandemic has led to speculation that the virus could have originated in the lab.

While Mr Pompeo's statement offered little beyond insinuation, the state department was on firmer ground when it accused the Chinese Communist Party (CCP) of preventing an investigation into the pandemic's origin.

"The CCP has prevented independent journalists, investigators, and global health authorities from interviewing researchers at the WIV," it said. The WHO team that travelled to China found itself at the centre of a propaganda battle, caught between a Chinese government determined to extol its leadership in fighting the virus and an outgoing US administration eager to shift blame from its own contentious pandemic response.

Landing in Wuhan after months of delay, the 13 members of the WHO team were whisked away for two weeks' quarantine before their fraught task of attempting to identify the origins of the virus from which two million have died.

The CCP has sought to reshape the narrative about where and when the pandemic began, while covering up early missteps which may have facilitated its global spread.

In the US, where more than 393,000 Americans have died, President Trump has repeatedly sought to blame Beijing for what he calls the Chinese virus.

Ever since the outbreak, Chinese authorities have attempted to control the narrative over the origins of the pandemic, claiming it existed abroad before it was discovered in Wuhan and at times promoting baseless conspiracy theories, including that the virus was a US military biological weapon.

They have also restricted access to foreign journalists. In December, a BBC team which visited Yunnan to investigate a mystery illness that killed three mine workers in 2012 reported being tailed by officers in unmarked cars, and having their route blocked by a "broken-down" lorry, which they were told had been placed across the road a few minutes before their arrival.

Yunnan, and the cave systems within its rolling jungle, is the site of major coronavirus research. WIV senior virologist Professor Shi Zhengli is known as "China's Batwoman" for her work there to predict and prevent outbreaks.

Prof Shi, her lab and the Chinese government have dismissed allegations that the virus might have leaked from the facility. But when she emailed the BBC telling them she would welcome WHO researchers to the WIV, the corporation later received a call from the lab's press office, saying she had been speaking in a personal capacity and her answers had not been approved.

Instead, the arrival of the WHO investigative team to Wuhan was stymied by months of delays and sensitive negotiations. When visa issues blocked the team's arrival earlier this month, speculation grew that Beijing was being deliberately obstructive. A Chinese foreign ministry spokeswoman sought to allay concerns, blaming a "misunderstanding". "There's no need to over-interpret this," she said.

But the frustration of WHO head Tedros Adhanom Ghebreyesus was clear when he issued a rare public rebuke, saying on Tuesday he was "very disappointed" that China had not authorised the entry of the team.

Last week China recorded its first coronavirus death in eight months as infections topped 138 new cases, the highest one-day jump since early March 2020, intensifying pressure on Chinese authorities to appear in control.

When as the WHO team departed for Wuhan, two of the 15 experts were barred from boarding their flight after testing positive for antibodies during a stopover in Singapore.

Mr Pompeo, meanwhile, continued rehashing allegations against the WHO first aired by President Trump, saying on Monday that the organisation "was corrupted by China's influence".

He repeated previous threats by President Trump to withdraw funding from the organisation, writing "we won't keep wasting taxpayer $$$ to subsidise Chinese influence operations."

By the time the WHO team is released from quarantine, the Trump administration will have left office, removing one source of pressure on the investigators. But another source will remain, however, as Chinese authorities seek to control the outcome of an investigation which is finally underway more than a year after the pandemic began./The Telegraph