South High School in Minneapolis reopened Friday with extra police and security on hand following Thursday's cafeteria melee.

The school called in additional resource officers, who are specially trained to deal with issues involving students, to help keep order Friday. There are also additional counselors present from the district's central office who will talk with students who witnessed the fight. 

Minneapolis police will launch an investigation into the incident and it will probably last several weeks. Possible charges range from disorderly conduct to rioting. 

Officials locked down the school Thursday after a cafeteria brawl involving 200-300 students broke out around 12: 45 p.m. Staff members had to call in a dozen police officers to get the fight under control; four people were sent to the hospital. 

The school will remain in a partial lockdown until further notice, and students will have to stay in their classrooms unless escorted by an adult. 

Students said the fight started because of racial tension between Somali-American students and students from other ethnic backgrounds.