Are we liable for defamation if we make allegations during an unemployment comp hearing?

Q. We fired an employee for stealing company property. While we didn’t catch her red-handed, the circumstantial evidence was overwhelming and we felt comfortable letting her go. The employee filed an unemployment compensation claim that we contested, and now a hearing has been scheduled before an appeals referee. We would like to say at the hearing that the employee is a thief, but we’re afraid we’ll face a defamation claim because we can’t absolutely prove this charge. Would that be a well-founded concern?