Updated with letter: Michigan receives notice of inquiry from NCAA about practice violations

"When reasonably reliable information has been obtained indicating a major violation may have occurred, the enforcement staff will undertake a review of the information in order to determine its credibility," Osburn wrote. "At that time, the involved NCAA member institution is informed by a notice of inquiry."

Typically, letters of inquiry detail the nature of the alleged violations, the parties involved and the approximate time frame for an investigation.

Michigan's letter, dated last Friday and addressed to president Mary Sue Coleman, said only that "the possible violations primarily involve the matters under review." The NCAA intends to complete its investigation by Dec. 31, the letter said.

In a statement, Coleman said the university is cooperating fully with the investigation.

"As I said at the onset of this review, we place the highest importance on the well-being of our student-athletes and the integrity of our program," the statement said. "We continue to work with the NCAA to ensure that a thorough and objective investigation occurs."

In August, Michigan launched an internal investigation into questions whether football coach Rich Rodriguez and his staff required players to practice more than the NCAA allotted 20 hours a week.

The university, with the help of law firm Lightfoot, Franklin and White, also is investigating whether coaches violated NCAA rules by attending offseason workouts.

Michigan athletic director Bill Martin, spokesperson Bruce Madej and assistant athletic director for compliance Judy Van Horn did not return phone calls seeking comment Monday.

Martin, who announced his retirement last Wednesday, effective next September, released this statement: "We continue to cooperate with the NCAA on this matter, which is why we reached out to both the Big Ten and the NCAA as soon as we heard the allegations. We remain committed to following both the letter and the intent of the NCAA rules."