The NCAA has joined Central Michigan in investigating a man resembling former Michigan staff member Connor Stalions who appeared on the Chippewas' sideline in team-issued gear for their Sept. 1 season opener at Michigan State.

Athletic director Amy Folan, in a statement to ESPN, confirmed that Central Michigan "continues its review of the matter in cooperation with the NCAA."

Folan announced last Tuesday that Central Michigan would investigate the man after receiving photos of him one day earlier. Stalions, at the center of the NCAA's investigation into Michigan for off-campus scouting and signal stealing, resigned from his position Friday after initially being suspended with pay, pending the outcome of the investigation.

The man in the images wore the same attire as Central Michigan's coaches and other sideline personnel, as well as sunglasses for the night game at Spartan Stadium. Stalions appeared on the Michigan sideline Sept. 2 for the Wolverines' opener against East Carolina.

Chippewas coach Jim McElwain said last week that Stalions' name did not appear on any list of credentials for the Michigan State game. According to NCAA rules, the "team area" during games includes a maximum of 50 non-squad members "directly involved in the game." Those not in full uniform wear special credentials assigned to the team area that are numbered 1 through 50. NCAA rules prohibit any other credentials in the team area.

"We obviously are aware of a picture floating around with the sign-stealer guy," McElwain said on Oct. 31. "Our people are doing everything they can to get to the bottom of it. We were totally unaware of it. I certainly don't condone it in any way, shape or form. I do know that his name was on none of the passes that were [given] out. Now we just keep tracing it back and tracing it back and try to figure it out."

The NCAA's involvement likely will extend the timeline for the investigative process and any potential discipline. Its findings could be included in a larger notice of allegations for Michigan, which has yet to be sent.

Anil Jain, a distinguished professor in the Department of Computer Science and Engineering at Michigan State and a nationally recognized facial recognition expert, believes it's "highly likely" that the images of the man wearing sunglasses and a hat on the Central Michigan sideline and a photo of Stalions on the Michigan sideline are the same person.

At ESPN's request, Jain and Steven Grosz, a Ph. D. student, used state-of-the-art commercial face recognition system to compare the two photographs. The system compared the images based on several facial characteristics -- Jain said they are trade secrets -- to provide a similarity score in the range of zero to 1. The higher the similarity score, the more likely is the two faces being compared are the same person.

Jain said the system produced a similarity score of 0.6 when comparing the two photographs. To validate that score, Jain and Grosz compared Stalions' photo to a database of more than 4,500 photos of white males.

"The reason why it's 0.6 is because there's a disguise," Jain told ESPN. "If I take an identical photo, it would be one. Even changes in the pose, illumination, expression, sunglasses, the match will never be perfect. Based on this analysis, the two images are of the same person with high confidence."

ESPN's Mark Schlabach contributed to this report.