NASHVILLE, Tenn. (AP) -- Federal officials are investigating Medicare billing practices at Vanderbilt University Medical Center.

According to The Tennessean, Vanderbilt officials acknowledged the probe by the U.S. Department of Justice and the inspector general of the Department of Health and Human Services.

The investigation dates back several months and includes requests for extensive records for services provided to Medicare patients in the four intensive care units at Vanderbilt.

Internal Vanderbilt memos reviewed by The Tennessean indicate the inquiry is focused on records showing when physicians were scheduled to staff the medical center's intensive care units.

Assistant Vice Chancellor John Howser said Vanderbilt is cooperating with federal officials and ready to address concerns that may be identified.