The woman who helped the FBI build its case against Illinois Gov. Rod Blagojevich says she knew "something was very, very wrong" but didn't have "personal knowledge" of corruption by the governor at the time she began wearing a wire as an FBI informant.

Pamela Davis told ABC News she decided to call the FBI in 2003 when she was president and CEO of Edward Hospital in Naperville, Ill., and was working to get approval from the state's health planning board to expand her facility. 

Davis said in the ABC News interview that she was told by the "bad guys" that the only way she would get approval for the hospital project was if she used a certain politically connected investment firm and contractor. 

The grandmother of six told ABC news she ignored the advice and picked a different contractor. Her proposal was denied.

"I was outraged that something as important to me as health care, something that was required, such an important service would have to fall under this type of terrible delay and expense and really just corruption," she said. 

And, that was when she decided to call the FBI -- triggering the investigation into corruption in Illinois politics that eventually led to Blagojevich's arrest.

"I really think he should step down immediately so that the state of Illinois can begin to function more appropriately and to go about doing the business of the state of Illinois for all of its citizens," she told ABC News.

Click here to read more on this story from ABC News.