Justin Bieber is in the crosshairs of the L.A. County Probation Dept ... because his Canadian arrest just set in motion a chain reaction that could land him behind bars.
Law enforcement sources tell us an investigation has been launched to determine if Justin's arrest for dangerous driving and assault constitutes a violation. We're told officials will contact law enforcement in Canada to verify the details of the incident.
Justin is currently on 2 years probation after pleading to misdemeanor vandalism in the egging case back in July.
Cops in Canada say Bieber got into a physical altercation with a paparazzo after his ATV collided with the photog's minivan.
We're told probation officers have 30 days to notify the court of any alleged violation. The court will then decide if Justin's probation gets revoked, and if he gets jail time.