First I want to say an email going out to everyone about possible sabotage in itself sounds odd/fishy to me. If such a thing was suspected then they would not try to give anyone time to build a story to or to cover their tracks. They would simply notify HR and management depending on the person who suspected it in the first place. Then HR would take appropriate action.
You say you and maybe one other person could have done what was being accused so at that point I would just gather some info for yourself in case you are questioned. But I would not reply to the email saying it was not you. There is no reason to bring attention to yourself.
As long as you know you did nothing wrong then you should be fine. The data will reflect that. Where you where when it happened what you were logged into at the time and so on. Unless some "Master Mind" has your credentials and used your identity to sabotage then you have nothing left to do but keep working until you finally leave after you notice time is up.
I would like to add some situations require a quick defense for example (Personal accusation of you specifically did something) as staying silent might be seen as accepting guilt. But when it is a group email saying something has happened but you are specifically asked if it was you then keep it that way and don't being it up.
Based on your comment:
It is an assertion sent to everyone involved in a project that was allegedly sabotaged(not the entire project but a tiny piece of it).
The accusation is against your group on a small portion of a single project. This sounds like even if someone did do something it cant be that big a deal it is likely not worth any anxiety you might be having.
One last note: As your decisions will ultimately affect you there are resources that can help you answer this question. If you are truly worried (IE. It is possible you made a mistake and it is being taken as sabotage) I would reach out to your internal resources with this question. IE Most companies HR can answer you but keep in mind that will likely be recorded in some official capacity.