When facing such large scale issues, communicating properly is very hard: Several teams might be investigating several possible root causes in parallel, and you might change your mind over time as to what is the most probable root cause.

So you might end up communicating something ("we think it comes from X, we're fixing it that way"), just to find yourself changing you mind a few minutes later.

Changing your message is usually not well perceived, even though that's actually normal during an investigation.

I would not like to be in charge of the communication. Finding the balance between saying too much or too little is tricky.