MADISON, Wis. -- The University of Wisconsin has cleared former basketball coach Bo Ryan of allegations that he had misused school resources while having an "improper personal relationship" with a woman, the school said.

Chancellor Rebecca Blank said in a statement Friday that Ryan was cleared in May following an investigation by athletics and the Office of Legal Affairs. The investigation was trigged by allegations the school received in February 2015 from the woman.

Ryan, who is married, retired abruptly following a game on Dec. 15, 2015. His departure "was entirely his decision," Blank said.

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The investigation was first reported by Deadspin on Saturday.

"The university determined on May 13, 2015 that Ryan did not utilize university resources during the course of the relationship in question," said the statement from Blank provided to The Associated Press on Saturday. "The university concluded the issue was a private matter."

An email sent by the AP to Ryan's attorney seeking comment from the retired coach was not immediately returned on Saturday evening.

In a statement to the Wisconsin State Journal sent from the attorney, Ryan said that his wife "Kelly and I believed that the University's findings concluded this matter."

"To be clear, this matter was absolutely unrelated to my retirement many months later," Ryan said. "In fact, I timed my retirement intentionally to assure that (interim coach) Greg Gard got his hard-earned opportunity to coach the University of Wisconsin basketball team."

According to the university's response to the woman in May, Ryan disclosed the relationship to the school in December 2014. The woman, in outlining allegations to athletic department officials, said she had ended her relationship with Ryan a couple months earlier.

A copy of the email sent by the woman in February 2015, with her name redacted, was released by the school. She said that she accompanied Ryan on recruiting trips to Kansas City, Las Vegas and other cities.

"I had a relationship with a woman who had no connection to the University of Wisconsin," Ryan said in his statement. "That relationship ended nearly 1 years ago. I revealed this issue openly to the University, and encouraged them to review any activity to assure them that no University resources were misused."

The school said its investigation included interviews with Ryan and the woman, along with a review of expense reports and email messages since 2009. Voicemails and text messages that may have been exchanged could not be reviewed because they no longer existed, the school said.

Allegations did not involve anyone on campus except Ryan, Blank said.

The basketball team plays Purdue on Sunday night in the regular season finale. Under Gard, the Badgers have won 11 of 12 games to get over a slow start in nonconference play with Ryan on the sideline.