A South Dakota state official said Thursday that a federal agency’s diagnosis of a recent leak in TransCanada Corp.’s Keystone pipeline could signal a systemic problem and could lead the state to revoke the permit that allows the company to operate the pipeline.

Gary Hanson, vice chairman of the South Dakota Public Utilities Commission, said in an interview Thursday that recent findings on the cause of the leak raised concerns about more widespread problems, because they showed the rupture in the pipe may have been caused...