All findings of fact made by the Labor Commissioner shall be based exclusively on the evidence, on matters officially noticed during the hearing, and upon the information received by the Labor Commissioner through investigation and examination made by its agents prior to or during the hearings, which shall be reduced to writing, sworn to, and filed and made a part of the record, or the testimony of such agents shall be taken under oath, in the discretion of the Labor Commissioner.
Okla. Admin. Code § 380:1-7-13