A low-level staffer with a military background has emerged as one of the linchpins in the NCAA investigation into Michigan's alleged sign-stealing operation, sources told ESPN on Thursday.

Connor Stalions, a football analyst with the Wolverines and a retired captain in the United States Marine Corps, is a person of interest in the investigation into whether No. 2-ranked Michigan violated an NCAA rule by scouting future opponents in person at games, sources said. The NCAA prohibited such scouting in 1994.

Sources said the NCAA enforcement staff's level of interest in Stalions is so significant it sought access to his computer as part of its investigation. Sources indicated that the process is underway, although it's uncertain what investigators will find.

Attempts by ESPN to reach Stalions were not returned. Michigan athletic director Warde Manuel did not return a request seeking comment.

A source told ESPN that the Wolverines have used an "elaborate" scouting system to steal signals from future opponents since at least 2021. With the ongoing NCAA investigation into Michigan recruiting and coach Jim Harbaugh potentially facing additional penalties there, this separate investigation could significantly increase his exposure to additional suspension.

In a statement Thursday, Harbaugh denied any knowledge of or involvement in the alleged scheme to steal opponents' signals through scouting trips to out-of-town games. Harbaugh said he would fully cooperate in any investigations and doesn't "condone or tolerate anyone doing anything illegal or against NCAA rules."

"I do not have any knowledge or information regarding the University of Michigan football program illegally stealing signals, nor have I directed any staff member or others to participate in an off-campus scouting assignment," Harbaugh said in the statement.

If the allegations are proven to be true, Michigan would have violated NCAA Bylaw 11.6.1, which states: "Off-campus, in-person scouting of future opponents (in the same season) is prohibited."

Michigan and the Big Ten were notified by the NCAA of the investigation Wednesday, and the conference said it had notified the Wolverines' future opponents, including Michigan State, which hosts Michigan in East Lansing on Saturday.

"The Big Ten Conference considers the integrity of competition to be of utmost importance and will continue to monitor the investigation," the conference said in a statement.

Even though Harbaugh said he had no knowledge of the alleged scheme, pursuant to NCAA Bylaw 11.1.2.1, a head coach is "presumed to have knowledge of what is occurring in his program and therefore, can be responsible for the actions of his staff and individuals associated with the program."

According to the NCAA, "if an allegation of Bylaw 11.1.2.1 is made against a head coach, then the coach must rebut the presumption that he had knowledge of what was occurring in his program and show that he did in fact set a proper tone of compliance and reasonably monitored the activities of his program."

"I have no awareness of anyone on our staff having done that or having directed that action," Harbaugh said in his statement. "No matter what program or organization that I have led throughout my career, my instructions and awareness of how we scout opponents have always been firmly within the rules."

Around Michigan's football building, Stalions is known to technically work in the recruiting department under director of recruiting Albert Karschnia. But a source said it was known in the building that he spent much of his time deciphering opponents' signals, often watching television copies of opponents' games. On Stalions' Instagram page, there are photos of him on the sideline next to two of Michigan's former defensive playcallers, Don Brown and Mike Macdonald.

"He had one role," said a source with knowledge of Michigan's staff.

What is crucial to the NCAA case isn't what Stalions did while breaking down television copies of games to learn and decode opponents' signals. It's whether or not illicit methods were used, which are alleged to include opponent scouting in different venues and was outlawed by the NCAA nearly three decades ago as a cost-cutting measure to bring more equity to the sport.

Sign stealing also violates NCAA rules if a team uses electronic equipment to decipher signals and relay the information to players and coaches. According to the 2023 NCAA football rule book, "any attempt to record, either through audio or video means, any signals given by an opposing player, coach or other team personnel is prohibited."

The allegations against Michigan appear to transcend the normal coach griping about opposing coaches stealing signals, as the depth of the allegations -- and the Big Ten's on-record affirmation of an investigation -- hint at something much more significant.

The allegations have rattled coaches and administrators around the Big Ten.

"This is worse than both the Astros and the Patriots -- it's both use of technology for a competitive advantage and there's allegations that they are filming prior games, not just in-game," a Big Ten source said. "If it was just an in-game situation, that's different. Going and filming somewhere you're not supposed to be. It's illegal. It's too much of an advantage."

Stalions, a graduate of the United States Naval Academy, was hired as an off-field analyst at Michigan in May 2022, according to a bio on his LinkedIn account. In the bio, Stalions wrote that he attempts to "employ Marine Corps philosophies and tactics into the sport of football regarding strategies in staffing, recruiting, scouting, intelligence, planning and more."

Among the skills Stalions wrote about on LinkedIn were "identifying the opponent's most likely course of action and most dangerous course of action" and "identifying and exploiting critical vulnerabilities and centers of gravity in the opponent scouting process."

The son of two Michigan alumni, Stalions enrolled at the Naval Academy and was a student assistant for the Midshipmen from 2013 to 2016. After being commissioned as a second lieutenant in the Marine Corps in 2017, Stalions worked as a graduate assistant at Navy before beginning his military training, according to his LinkedIn account.

While he was stationed at Camp Pendleton in California, Stalions wrote, he served as a volunteer assistant coach at Michigan from May 2015 to May 2022.

"On top of my daily duties as a Logistics Officer leading [40-plus] at a time, I volunteered for the Michigan football staff, flying back [and] forth on my own dime, assisting the defensive staff," Stalions wrote.

In a profile of Stalions on the website Soldiers to Sidelines in January 2022, he said he purchased a house and rented each of the bedrooms on Airbnb, while sleeping on the couch, to help pay for his travel to Ann Arbor, Michigan.

Stalions retired as a captain in the Marine Corps in May 2022 and joined Michigan's staff as an off-field analyst.

Harbaugh already faces NCAA charges of failure to cooperate and head coach responsibility related to alleged recruiting violations during the COVID-19 dead period. A violation by a member of his coaching staff could trigger another charge of head coach responsibility, which could be a Level I violation.

The NCAA Committee on Infractions rejected a four-game negotiated suspension for Harbaugh in the recruiting case, and Michigan self-imposed a three-game suspension. With that case still needing to be resolved, an additional head coach responsibility charge based on alleged signal stealing would significantly increase his exposure to additional punishment, including a longer suspension.

Michigan still is facing four Level II violations, which are considered less serious, from those alleged violations. The NCAA is not expected to announce a ruling in that case until 2024.

ESPN's Adam Rittenberg contributed to this report.