No charges yet as the FBI continues to investigate a 2016 theft of more than $300,000 in cash from Mayo Clinic by an employee.

Mayo Clinic reported the theft in its 2017 IRS filing in November.

"In 2016, a theft of cash by an employee responsible for handling cash was discovered. It is estimated the loss exceeded $300,000. Additional tangible items were also discovered that may be stolen property," according to Mayo Clinic in the filing. "The theft was reported to law enforcement, the employee terminated and improved cash practices were implemented."

When asked about the status of the case earlier this month, Susan Barber Lindquist of Mayo Clinic gave the same answer as in November.

"It’s an ongoing investigation, so I still can’t offer other details," she wrote in an email on March 5.

The FBI also declined to comment other than to say they are still investigating.

It's unclear what is causing the case to drag on for so long. Mayo Clinic's report says the thief was identified and fired.

And yet, no charges have been filed more than a year after the theft was discovered.

It is unusual for Mayo Clinic to mention a theft by an employee publicly. In this instance, the IRS rules required the report be made.

The section in the 990 form, filed by all nonprofits with the IRS, asked about any "significant diversion" of assets. Any amount of $250,000 or more is considered "significant" in this context by the IRS. When Mayo Clinic answered it was aware of such a diversion, it then had to explain the circumstances.

"A diversion of assets includes any unauthorized conversion or use of the organization's assets other than for the organization's authorized purposes, including but not limited to embezzlement or theft. Report diversions by the organization's officers, directors, trustees, employees, volunteers, independent contractors, grantees (diverting grant funds) or any other person, even if not associated with the organization other than by the diversion," according to IRS directions.