ABINGDON, Md. -- A Harford County schoolyard brawl between two rival groups sent four people to hospitals Thursday night.

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Investigators said the fight that happened on the grounds of William S. James Elementary School in Abingdon was planned and stemmed from an argument a few days before.

As many as 30 people, the majority of whom were teenagers, got into a fight in the confines of a caged asphalt playground, the Harford County Sheriff's Office said. Investigators likened it to a clash reminiscent of a scene out of "West Side Story" and the movie "The Outsiders."

Officials said they were alerted to the brawl by a call placed to 911.

"One group brought baseball bats and golf clubs, and a large fight ensued," said Sgt. David Betz of the Harford County Sheriff's Office.

All but two people involved in the fight fled the scene before police arrived. Authorities said they found a man lying on the ground bleeding from the head and complaining of back pain. A state police Medevac took him to Shock Trauma.

A juvenile was transported to Bayview Medical Center with facial injuries, police said. Two other teens went to Upper Chesapeake Medical Center for treatment.

Police said they're recovered some of the bats and golf clubs. Charges have not yet been filed.

Officials said they're still trying to find out what caused the brawl. Police have ruled out school-related, gang-related and racially motivated violence.