Mayo Clinic says it discovered last year the theft of more than $300,000 by an employee who was responsible for handling cash at the Rochester-based health care system.

Mayo says “additional tangible items” were discovered that might also be stolen property, according to a regulatory filing made public this month.

The theft “took place in Rochester and was discovered and reported to the FBI in 2016,” said Mayo Clinic spokeswoman Susan Barber Lindquist via e-mail. “It’s an ongoing investigation, so I can’t provide other details.”

An FBI spokesman had no comment.

Mayo Clinic reported the theft as part of its annual filing as a nonprofit group with the Internal Revenue Service. The filing, which Mayo made public last week, asks nonprofits to report any significant diversion of assets.

“It is estimated the loss exceeded $300,000,” Mayo Clinic said in the filing. “The theft was reported to law enforcement, the employee terminated and improved cash handling practices were implemented.”

In 2016, Mayo Clinic posted $475 million in net income on $11 billion in revenue. Beyond Minnesota, the health system has operations in Arizona, Florida, Iowa and Wisconsin.