It does not have to even be a big conspiracy. China does not always seem to be kind to people who mess up.
Example>>>>
The death penalty handed out to a former Chinese finance chief found guilty of corruption has been heavily criticised by human rights groups.
Lai Xiaomin was arrested in 2018 on charges of taking 1.8bn yuan (£200m, $280m) in bribes over a 10-year period.

It seems perfectly reasonable that those in charge of the lab would try to cover it up, especially if they were careless or doing research they were not supposed to. From there the cover up could continue, as each in the cog does not want to face the consequences.