The international scientists dispatched to China by the World Health Organization to find out where the coronavirus came from says on Wednesday the search has stalled.
Meanwhile, a US intelligence review ordered up by President Joe Biden proved inconclusive about the virus's origin.
In a commentary published in the journal Nature, the WHO-recruited experts said the investigation of the origin is at "a critical juncture" requiring urgent collaboration but has instead come to a standstill.
They noted among other things that Chinese officials are still reluctant to share some raw data, citing concerns over patient confidentiality.