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.

The firm presented evidence to the NCAA and suggested Connor Stalions, a low-level staffer who has been suspended by Michigan, was not the only person on staff aware of the scheme, according to the report. A second person with knowledge of the situation confirmed to the AP that a firm provided the NCAA with evidence, including photographs, videos and documents, that initiated the association’s investigation.

It was unclear who hired the firm to investigate Michigan. Both Michigan and the Big Ten have acknowledged the investigation.

Harbaugh, who is facing unresolved NCAA violations in a separate case tied to recruiting, has denied any knowledge or involvement in impermissible scouting of opponents.

The Wolverines (8-0, 5-0 Big Ten) have won consecutive conference championships and reached the playoff semifinals each of the last two seasons. Michigan's next game is Nov. 4 at home against Purdue.

The NCAA does not directly ban the stealing of signs, but there are rules against using electronic equipment to record an opponent’s signals and in-person, advanced scouting of future opponents in season. There are also rules against unsportsmanlike or unethical activities by coaches, and head coaches are generally considered to be responsible for violations that occur under their watch.

Stalions appeared to be purchasing tickets to the games of Michigan opponents and sending people to obtain video of the sideline signals used for calling in plays. There are images and video from Michigan games over the past two seasons with Stalions on the sideline, standing near Wolverines coaches. Stalions was hired in 2022 as part of the recruiting staff.

Multiple Big Ten schools have found records of tickets being purchased to their games in Stalions’ name over the past three seasons, and records show tickets purchased in Stalions’ name to the last two SEC championship games.

According to the Post, the investigative firm told the NCAA that cellphone videos from the games were uploaded to a computer drive accessed by Stalions and other Michigan assistants and coaches, though there was no evidence presented to the NCAA directly linking Harbaugh to the scheme.

The scandal has revived a desire by many coaches for the NCAA to clear the way for technology to be used for coaching staffs to communicate with players on the field, as is done in the NFL.

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AP College Football Writer Ralph D. Russo contributed. Follow Larry Lage at https://twitter.com/larrylage

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AP college football: https://apnews.com/hub/college-football