Students and teacher held hostage at US high school
An administrator at Marinette High School called the authorities shortly after 1500 (2100 GMT) to say a student with a handgun had taken over a room.
Marinette Police Chief Jeff Skorik told reporters that hostage negotiators were inside the school, and that there had not been any threats or demands made.
No gunfire or injuries have been reported since the stand-off began.
The police have blocked off roads near the school, and local media report that a Swat team has been called to the scene from Green Bay.
It is not known if the gunman was supposed to be in the classroom where the hostages are being held. He does not have any police history.
Chief Skorik said that all contact between the armed student and the negotiating team had been through the female teacher held hostage.
"We have no idea as far as motivations at this point," he said. "We want to encourage this young man... to come out."
Parents have been asked to go to the local courthouse if they have not been in contact with their children. Meanwhile, dozens of people continue to gather near the school, hoping to find out what is going on; Kaziform refers to BBC News.