What circumstantial evidence?
https://www.wsj.com/articles/the-world-needs-a-real-investig...
There's also been a string of academic preprints and articles, like
https://arxiv.org/ftp/arxiv/papers/2102/2102.03910.pdf
The authors tend to be kind of fringe, not surprisingly given the reputational cost (and given that if a lab origin is ever confirmed, many of the techniques that top researchers have spent their lives mastering will probably become illegal). A lot of very senior virologists are on the record as open to the possibility of a lab escape, though, for example:
> Baric said he still thought the virus came from bats in southern China, perhaps directly, or possibly via an intermediate host, although the smuggled pangolins, in his view, were a red herring. The disease evolved in humans over time without being noticed, he suspected, becoming gradually more infectious, and eventually a person carried it to Wuhan “and the pandemic took off.” Then he said, “Can you rule out a laboratory escape? The answer in this case is probably not.”
https://nymag.com/intelligencer/article/coronavirus-lab-esca...
I don't recommend that article in general; the author uses his talents as a novelist to paint a more vivid picture than I believe the evidence justifies. I do trust him to faithfully print the quote, though.