Reminds me of the 1984 Rajneeshee bioterror attack[1] which was investigated by the CDC and also blamed on sick workers[2] because they were the first to fall ill.
Only after internal conflicts between the Rajneeshes rose up to the surface, it turned out it was an intentional biological attack.
Netflix' Wild Wild Country is a good that covers it (eventhough it is too long, and way too nice towards the Rajneeshees).
[1] https://en.wikipedia.org/wiki/1984_Rajneeshee_bioterror_atta...
[2] https://www.nytimes.com/1984/10/21/us/ill-handlers-suspected...