Technically they should release news as soon as possble but practically they can sit on information until it becomes obvious to the regulators that they are witholding.

They do not report visuals but they can see if there is something to be seen. Having that info they can decide to not send cores for a while or send them and pay extra for extra fast assays. Having received the results, who other than regulators is going to force them to release?

And even the regulators must know or strongly suspect that information is being held back otherwise they are as much in the dark as ordinary investor.