Edmonton police say a dispute over an expired bus transfer led to an attack on an ETS driver on Friday.

The Edmonton Transit driver was assaulted by a man at around 2 p.m. in the Castledowns area, police spokesperson Cheryl Sheppard said in an email.

The driver suffered non-life-threatening injuries and was taken to hospital, where he was treated and released.

City spokesperson Katherine Heath-Eves said the suspect escaped. She could not say what kind of weapon was used, or whether the bus was moving at the time.

No passengers on the bus were injured.

ETS has launched a safety investigation, and is offering the driver counselling.

Police are now reviewing ETS surveillance footage in hopes of identifying a suspect.