Chris Brown Hit-and-Run Probe -- Prison On the Line

BIG TROUBLE for Chris Brown -- TMZ has learned the LAPD is investigating the singer, and it could trigger a probation violation that could land him in prison.

What could have been a simple fender bender earlier this week is now a full-blown hit-and-run investigation ... after Chris Brown allegedly refused to give the driver he rear-ended his driver's license #. We're told he also gave the woman incorrect insurance info.

What's more ... we're now told Chris copped an attitude when the woman pressed him for his ID, before refusing to ante up his DL.

Brown is on probation for the Rihanna beating, and one of the conditions is that he obey all laws. If there's probable cause to believe he broke the law by leaving the scene without fully disclosing information required by law, his probation could be violated and Chris could go to prison for up to 4 years.