Is it possible to delete event logs?

Chris.W.565

I have grades that have disappeared in the brightspace gradebook, and when I tried to investigate, there are no 'event' logged. The submitted files for the assignment in question have all been 'read', supporting the TAs assertion that they graded the assignment, but the grades are all gone. I am concerned that someone has tampered with the grades, and I attempted to review the event log but they are all empty. Is it possible that someone could delete the event log?