ANN ARBOR, Mich. (AP) — NCAA investigators interviewed members of Michigan football coach Jim Harbaugh’s staff Thursday about a sign-stealing scheme, a person familiar with the governing body’s visit told The Associated Press.

The investigation has rocked the undefeated and second-ranked Wolverines on their march toward a potential spot in the College Football Playoff. The interviews were confirmed by the person who spoke to the AP on condition of anonymity because no one was authorized to speak publicly about the details.

The NCAA inquiry was triggered by an outside firm’s investigation, which turned up videos of and documented plans and budgets for impermissible scouting of opponents. The Washington Post reported the firm obtained computer drives maintained and accessed by multiple Michigan coaches.