Agents seized a significant number of documents relating to the practice of Dr. Phillip Gabriele of the Gabriele Eye Institute on Thursday.

Authorities say this is an investigation into Medicare and Medicaid fraud.

Federal agents arrived at Gabriele’s Granger home at 7:30 a.m. At the same time, they executed search warrants at Gabriele’s offices in Mishawaka, South Bend and Elkhart.

At all four locations, agents seized a significant number of documents relating to his practice.

Many of the agents were from the U.S. Department of Health and Human Services, office of inspector general. That office investigates Medicare fraud.

A large amount of investigators from the Indiana Attorney General's Medicaid Fraud Control Unit also were at the offices.

Federal authorities aren't saying much about what led to this investigation. But WSBT News found the most commonly investigated types of fraud include:

• Billing for nonexistent patients or patients of other providers;

• Billing for services not provided;

• Billing for unnecessary treatment or testing;

• Accepting kickbacks from referrals; and

• Making a patient pay more than a Medicaid-approved co-payment for services.

Dr. Phillip Gabriele was at his home when the agents arrived, but left with no comment about the situation.

Once again, federal authorities aren't saying much about what led to what happened, and no one has been arrested.

The Assistant U.S. Attorney for Northern Indiana says the investigation continues.