1 Pa. Code § 35.128
At a stage of the hearing the agency head or the presiding officer may call for further evidence upon an issue, and require the evidence to be presented by the party or parties concerned or by the staff counsel, either at that hearing or at the adjournments thereof. At the hearing, the agency head or the presiding officer may, if deemed advisable, authorize a participant to file specific documentary evidence as a part of the record within a fixed time, expiring not less than 10 days before the date fixed for filing and serving briefs.
1 Pa. Code § 35.128
This section cited in 1 Pa. Code § 35.131 (relating to recording of proceedings); 1 Pa. Code § 35.162 (relating to reception and ruling on evidence); 4 Pa. Code § 607a.17 (relating to additional hearings and evidence); 10 Pa. Code § 3.11 (relating to hearing rules); 25 Pa. Code § 1021.126 (relating to limiting number of witnesses and additional evidence); 34 Pa. Code § 131.53 (relating to procedures subsequent to the first hearing); 34 Pa. Code § 131.53a (relating to consolidated hearing procedures); 34 Pa. Code § 131.57 (relating to compromise and release agreements); 34 Pa. Code § 131.202 (relating to first hearing information and stay); 34 Pa. Code § 131.203 (relating to hearing procedures); 40 Pa. Code § 15.46 (relating to hearings); 52 Pa. Code § 5.404 (relating to additional evidence); 52 Pa. Code § 1005.144 (relating to additional evidence); 61 Pa. Code § 703.31 (relating to disposition of petitions); and 61 Pa. Code § 703.34 (relating to hearing procedure).