I've been called in for police questioning. Will my visa be cancelled just because I'm under investigation?

No. Being investigated, or even arrested, does not by itself cancel your visa. Status problems usually arise from the final outcome — a conviction, certain sentences, or the nature of the offense. That said, the investigation stage is when the outcome is shaped. What you say in your first interview can determine whether the case is dropped, settled, or sent to trial. Speak with a defense lawyer before you attend.