University of Mississippi football coach Hugh Freeze announced his resignation Thursday night after school officials cited personal conduct issues that included a one-minute telephone call to a number associated with a female escort service, USA Today reported.

The phone call was raised as a potential issue in a legal battle between the school and former Rebels coach Houston Nutt, who filed a lawsuit July 12 alleging that Ole Miss violated the terms of his severance agreement. Nutt’s attorney, Thomas Mars, sent an email to Ole Miss general counsel Lee Tyner, mentioning a “phone call Coach Freeze made that would be highly embarrassing for all of you and extremely difficult to explain,” USA Today reported.

School Chancellor Jeff Vitter, announcing Freeze's resignation at a news conference, called it a "sad day" for the university.

“While Coach Freeze served our university well in many regards during his tenure, we simply cannot accept the conduct in his personal life that we have discovered” VItter said.

Athletics director Ross Bjork said the resignation did not involve NCAA allegations but was based on a pattern of inappropriate conduct, USA Today reported.  Ole Miss put a self-imposed postseason ban this season and is already is operating with self-imposed scholarship reductions. The school faces the outcome of an NCAA investigation that traces back to 2012, ESPN reported.

Bjork said the phone call was brought to his attention last week.

“Because the call lasted less than one minute and did not appear at the time to be part of a pattern, we initially attributed this call to a misdialed number,” Bjork said. “We proactively looked into the rest of his phone records. In our analysis, we discovered a pattern of conduct that is not consistent with our expectations as the leader of our football program. As of yesterday, there appeared to be a concerning pattern.”

Freeze went 39-25 at Ole Miss and took the Rebels to a Sugar Bowl victory. He also guided Ole Miss to a pair of victories against Alabama when the Crimson Tide was ranked in the top three nationally.

Matt Luke, the team's co-offensive coordinator and line coach, was named interim coach on Thursday.