S.D. Codified Laws § 49-13-4
If any telecommunications company or motor carrier complained of pursuant to § 49-13-1 does not satisfy the complaint within the time specified, or there appears to be any reasonable grounds for investigating the complaint, the commission shall investigate the matters complained of in the manner the commission considers proper. The commission may, at any time, institute an inquiry or investigation on its own initiative in any case, involving any matter over which the commission has jurisdiction concerning a complaint that is authorized to be made and filed with the commission by any provision of any law of this state, or concerning any question which may arise, or relate to the enforcement of any provision of any law of this state.
SDCL 49-13-4