ABC News’ Candace Smith reports:

Wisconsin Gov. Scott Walker says he has no details of what the FBI was looking for this week when agents raided the home of Cynthia Archer, a former top aide in his office and a current legislative liaison with the state Department of Children and Family Services.

Witnesses saw FBI agents taking pictures of the property and saw them walk out with one box according to ABC station WLS-TV in Chicago.

Amid calls from his opponents to explain what the investigation is about, Walker told ABC affiliate WKOW-TV in Madison, Wis., that he had not spoken out previously because he simply does not know that much.

“Well, it’s hard to tell. We don’t know what exactly is involved there until we know any more,” Walker said. “We don’t know any details. We don’t know what it may or not be a part of.”

According to a report in the Milwaukee Journal Sentinel, the raid is just the latest in a secret ongoing investigation that focuses on whether county staffers in Walker’s office did political work on taxpayers’ money. The action appears to come in the wake of the confession of one of Walker’s staffers, admitting to anonymously posting pro-Walker comments on websites while on county time.

Archer said she complied with the requests of the FBI agents who came to her home, and said she had done nothing wrong.

“If they need anything, I’ll give it to them,” she told The Associated Press

When contacted by ABC News, the Milwaukee Bureau of the FBI declined to comment on the raid or ongoing investigation.

Archer was one of Walker’s most trusted allies before she abruptly resigned her post last month as deputy secretary of the agency that oversees state contracts.

Another who left the governor’s administration without warning is Tom Nardelli, who was Walker’s chief of staff before resigning this summer. According to the Sentinel report, the investigation focuses on him as well as Archer.

Since the resignations, Democratic lawmakers introduced a bill that would repeal changes that allowed the governor to replace civil service positions in state agencies with political appointees. Archer’s job is one of such civil service positions.

Democratic Assembly Minority Leader Peter Barca told the AP that the bill would ensure political cronies would not be working for Walker or future governors.

Though officials have raided Walker’s staffers before, only one investigation has resulted in a conviction. William Gardner, president and CEO of Wisconsin & Southern Railroad Co., was found guilty of two felonies related to exceeding campaign donation limits and laundering campaign donations to Walker.

Walker’s campaign returned the donations Gardner gave.