Federal authorities last week warned dozens of Shawano area residents they may be targeted for potential violence or harassment.
Authorities have not disclosed how the list of names was obtained or why they believe there was a threat to the persons it named.
The FBI acknowledged the possible threat and the investigation in a brief statement made available to news media Wednesday.
"The FBI made a public announcement to 60 potential victims in Shawano, Wis. on Wednesday, Nov. 5. The FBI advised these individuals that they were potential victims of an implied threat that was discovered as part of an ongoing investigation," said the statement, read by spokesman Leonard Peace. "Pursuant to FBI policy, the potential victims were notified of the implied threat."
The statement added: "This is an ongoing investigation and specific details of this case will not be released at this time."
However, somewhat more information was disclosed to about 40 of the possible victims at the announcement last week held at a local hotel.
Three of the 60 people are considered primary potential targets, said Ray Greco, the supervisory senior resident agent for the FBI in Green Bay.
Asked how seriously the FBI was taking the alleged threat, Greco said it is currently the top priority of the Green Bay field office and all available resources, including additional agents, would be assigned to the case if necessary.
"We're working it very aggressively," he said.
He advised those whose names were on the list to "be vigilant" and report any suspicious activity to local law enforcement. Shawano Police Chief Ed Whealon and Shawano County Sheriff Randy Wright also attended the meeting, along with several officers and deputies.
Several people named in the list spoke off the record to a Leader reporter, saying they were frustrated by the lack of detail offered by the FBI and the vague nature of the alleged threat.
Three employees of the Shawano Leader are among those who were notified at the meeting on Nov. 5.
Shawano Mayor Lorna Marquardt has declined to discuss the matter.
"It's an ongoing federal investigation and I can't comment," Marquardt said Wednesday.
Despite the ongoing investigation, news about the list was made public by several out-of-town media organizations Wednesday, forcing authorities who had previously spoken only off the record to publicly confirm the investigation.
News departments and camera crews from five TV stations, mostly from Green Bay, descended on City Hall Wednesday night for the Common Council's monthly meeting.
The meeting, which is usually broadcast on the local public service channel, could not be aired Wednesday night because there was no room for the city's camera, according to Director of Public Works Rick Stautz, who normally runs the city camera for the meetings.
Visitors to the council meeting were required to go through beefed-up security from Shawano Police officers before entering City Hall.
The city had begun tighter security last week, the same day the FBI held its meeting informing those whose names were on the list. Since the middle of last week, City Hall visitors had been required to enter through the adjacent Police Department entrance.
Greco said additional details could not be released without compromising the investigation and the FBI asked those informed of the list to limit its discussion to immediate family members.
However, the existence of the list has become known to the community and rumors about the list have begun to circulate.
Greco said the law requires the FBI to notify anyone who could be targeted for some kind of crime. However, he said, the FBI could not offer them protection.
