A 17-year-old boy is in hospital with serious injuries after a stabbing near the Pickering GO station.
Police said the incident happened around 9:30 a.m. on Wednesday.
Police said the boy was stabbed while riding a Durham Regional Transit bus.
The K-9 unit has been called to the scene to assist in the search for the suspect.
There has been no word on what prompted the altercation.
Police are asking anyone with information about the incident to call the West Division Criminal Investigations Bureau at 1-888-579-1520.