Halfway through the 90-day review into the origins of Covid-19, the US intelligence community is still divided on whether the disease leaked from a laboratory in China's Wuhan city or was transmitted from animals to humans.
Little new evidence has emerged in the US' ongoing investigation into the origins of Covid-19, CNN reported citing multiple sources familiar with the review.
Read: Scientists reject Covid-19 conspiracy claims over lab origin
However, top Biden administration officials such as National Security Adviser Jake Sullivan and federal agencies like the CIA now think the laboratory leak theory is plausible, marking a shift in their initial thinking.
In recent months, the idea that the pandemic started somehow in a laboratory – and perhaps involved an engineered virus – has gained traction, especially with President Joe Biden ordering a review of US intelligence to assess the possibility in May.
The US leader gave the intelligence community 90 days to complete the report.
Read: EXPLAINER: The US investigation into COVID-19 origins
China has struck back aggressively, arguing that attempts to link the origins of Covid-19 to a lab are politically motivated and has suggested that the outbreak might have started abroad.
Meanwhile, the head of the World Health Organization (WHO) on Thursday acknowledged it was "premature" to rule out a potential link between the Covid-19 pandemic and a laboratory leak.
WHO Director-General Tedros Adhanom Ghebreyesus said getting access to raw data had been a challenge for the international team that travelled to China earlier this year to investigate the source of Covid-19.
He said there had been a "premature push" to rule out the theory that the virus might have escaped from a Chinese government lab in Wuhan – undermining the WHO's own March report, which concluded that a laboratory leak was "extremely unlikely."
The first human cases were identified in Wuhan. Tedros told reporters that the UN health agency is "asking China to be transparent, open and cooperate, especially on the information, raw data that we asked for at the early days of the pandemic."