(a) Record. (1) The record of a hearing consists of the transcript of testimony or summary of testimony and exhibits together with all documents filed in conjunction with the hearing.

(2) If a hearing has been held on a referred issue of fact pursuant to § 4.337 or § 4.415, this record is the sole basis for decision on the referred issues of fact that are involved, except to the extent that official notice may be taken of a fact as provided in paragraph (b) of this section.

(3) Where a hearing has been held in other proceedings, the record made is the sole basis for decision except to the extent that official notice may be taken of a fact as provided in paragraph (b) of this section.

(4) In any case, no decision after a hearing or on appeal may be based upon any record, statement, file, or similar document that is not open to inspection by the parties to the hearing or appeal, except for documents or other evidence received or reviewed pursuant to § 4.31(d).

(b) Official notice. The presiding officer or an Appeals Board may take official notice of the public records of the Department of the Interior and of any matter of which the courts may take judicial notice.