Seven students were arrested and five have been charged after multiple fights between groups of students broke out Thursday morning at North High School in North St. Paul.

About 8:10 a.m. Thursday, a school resource officer with the North St. Paul police called for assistance as fights broke out at the start of the school day near the cafeteria, said North St. Paul Capt. Dustin Nikituk. Six squad cars, including Maplewood police, responded to the school.

"It was chaos," Nikituk said. "Kids were fighting and yelling."

Seven male students directly involved in the fights were arrested. The Ramsey County attorney's office confirmed that four students, one 14 and three 15, are charged with third-degree riot. The fifth, 16, is charged with obstructing the legal process. Details of the charges were not released because the students are juveniles.

A 14- and 15-year-old remain in custody pending further investigation.

Other students who were involved in some way were released at the scene to parents and guardians, and also could face prosecution, Nikituk said, adding that up to 10 could be charged.

One student was transported to a hospital for noncritical injuries. The student was being monitored because of a pre-existing medical condition, said Jennifer McNeil, spokeswoman for the North St. Paul-Maplewood-Oakdale School District.

Police said it took about an hour to defuse the situation. No weapons were involved.

The motive remains under investigation, Nikituk said, adding that police believe there was one main reason for all the fights.

Nikituk said police haven't responded to any incidents in recent months that could be related to Thursday's melee. Police added extra patrols to the school grounds Thursday.

Students who see or hear of any threats or unusual activity at school should report them to an administrator, Nikituk said. McNeil said Friday that staff members also joined in the effort to calm the situation, and succeeded in confining the skirmishes to the area near the cafeteria. She did not believe any staff members were injured.

"The day flowed smoothly after that," McNeil said.

She said the district also is investigating the incident.