Often its best to say nothing. Anything you say to a county fraud investigator or in a civil ADH hearing (see below) can be used against you later. If you say or sign something, it can be held against you. If you answer questions, anything you say can be used against you.
But, under the 5th Amendment to the U.S. Constitution, you have the right to not answer questions! The 5th Amendment means you don’t have to talk to the county fraud investigator. You don’t have to testify against yourself in a criminal case or an ADH hearing. It may help to talk to a lawyer about this issue.