"We did not have any concrete information that this involved gangs at the time this occurred and over the weekend," Lt. Todd LePine said Monday morning. "It's not until the last hour, hour and a half that that information came to us."
In Thursday's fight, police said one student had an injured jaw. Another was knocked down. At least one citation was given for disorderly conduct. Officers are still interviewing witnesses and going over school surveillance video.
Superintendent Michelle Langenfeld said parents were notified through email and robocalls on Saturday.
"We will not tolerate disruptions like this or any potential gang activities or aggressive behaviors in our schools," she said. "Each school in Green Bay Area Public Schools is a safe place for kids and we will keep it that way."
Despite no more specific threats of violence, school officials said the heightened security measures will stay in place for as long as they feel necessary for the safety of all students.
"There was one inside the school and one outside," Preble freshman Daniel Cortez told Local 5.
Cortez didn't see either fight happen, but he said it's been a big topic of conversation among students.
"They say when it's two or more people, that's a gang already," he added. "But it's like a lot of people fighting and it's always the same people, so it's probably a gang."
Police said they are still in the early stages of their investigation. Parents will be notified when any further information becomes available.