Unless I'm missing something, is there any non-circumstantial evidence that this is true? All I've seen for the past year(!) is "it's not a coincidence that these two things happened in the same place" - which isn't science.
It is part of divining what type of experiment or investigation is indicated to unearth direct evidence.
From the opinion piece in Proceedings of the National Academy of Sciences I linked elsewhere in this thread:
""" An investigative process should be transparent, collaborative, international, and, to the extent possible, devoid of political interest. Recent, productive scientific collaborations between the United States and China, for example, provide hope that such a process can be achieved. But the kind of effort required will need to expand far beyond what’s taken place so far, and nations other than the United States and China will need to be involved. Conflicts of interest by researchers, administrators, and policymakers on all sides must be revealed and addressed, and all relevant global constituencies must be included. """