(a) At a Tribe's request;

(b) As part of an investigation undertaken when the Tribe notifies the Secretary of a violation or breach;

(c) As part of an investigation undertaken because of a petition submitted under subpart E of this part;

(d) As follow-up to a determination that harm or the potential for harm to a physical trust asset, previously identified in a periodic review and evaluation, exists; or

(e) As the Secretary determines appropriate to carry out the Secretary's trust responsibilities.