There is mounting pressure on Big Ten Commissioner Tony Petitti from football coaches to discipline Michigan and coach Jim Harbaugh for an alleged sign-stealing scheme that has cast a cloud over the second-ranked Wolverines as the postseason approaches.

Coaches were angry and expressed frustration during a call with Petitti over a lack of action by the conference as mounting evidence supports allegations that a Michigan staffer sent people to games to do impermissible advanced scouting of opponents, according to two people with knowledge of Wednesday’s meeting, one who listened in on the call and another who participated.

The people spoke to The Associated Press on Thursday on condition of anonymity because the conference was not making its internal discussions public.

This week’s initial College Football Playoff rankings, where Michigan was ranked third, stoked coaches’ outrage over the inaction.

“They said it was an NCAA issue and not a CFP issue. It’s a football issue,” said the person who was on the call.

During a regularly scheduled video call with Big Ten athletic directors last week, Petitti first heard complaints from within the conference and calls for the league to hand down some punishment. The call with coaches Wednesday was also regularly scheduled, but it was dominated by talk of the current allegations against Michigan.

A previously unscheduled meeting with Pettiti and the Big Ten’s athletic directors was set for later Thursday, one of the people said. Both people said Petitti suggested a possible follow-up call with the coaches on Sunday.

NCAA rules do not ban the stealing of signs, but bylaws do preclude in-person, in-season scouting and the use of electronic equipment to record opponents’ signals. The allegations against Michigan are elaborate.

Michigan and the Big Ten have acknowledged the NCAA is investigating the Wolverines football program. Michigan has suspended low-level staffer Connor Stalions.

Multiple Big Ten schools have found tickets purchased in Stalions’ name to their games over the last three seasons. A person with knowledge of the situation told AP tickets to the last two Southeastern Conference championship games were also purchased in Stalions’ name.

The NCAA investigative process is slow moving and is likely to extend well past the Jan. 8 CFP national championship game.

Even if NCAA enforcement was able to expedite the case and provide Michigan an official notice of allegations soon, the school would still have 90 days to respond. A hearing would come after that.

What kind of penalties the Big Ten could hand down are unclear. Big Ten bylaws do provide the commissioner more leeway to act quickly on matters of sportsmanship and competitive integrity.

Petitti would be acting with limited information. The NCAA has not shared much of its evidence with the Big Ten, said one of the people, who has knowledge of that situation. Big Ten schools have provided records for ticket purchases in Stalions’ name and even some video surveillance footage of people sitting in those seats, holding cellphones pointed toward the field, presumably for video recording.

Harbaugh already served a school-imposed, three-game suspension at the start of the season for an unrelated NCAA violations case.

Michigan (8-0) hosts Purdue this week before finishing its regular season with road games against No. 11 Penn State and Maryland and the traditional season finale at home against No. 3 Ohio State (No. 1 CFP).