PORTLAND, Ore. -- Springfield police are looking for a suspect accused of stabbing a boy following a dispute on a bus.

Sgt. David Lewis says Tuesday's incident began when two groups of young men got into an altercation on the bus. One group was ordered out of the vehicle and the second group left the bus after a short distance.

Lewis says the groups clashed again, resulting in the victim getting stabbed. He was treated at the scene and then taken by ambulance to the hospital, where he remains Wednesday.

The suspect is believed to be in his late teens or early 20s.