The wheels of justice are turning quickly for Chris Brown ... we've learned the L.A. County Probation Dept. has launched an investigation into Chris Brown's D.C. arrest to determine if it constitutes a violation of his probation in the Rihanna beating case.
We've learned -- and this is pretty ironic -- the Probation Dept. found out about the arrest from Chris' lawyer, Mark Geragos. We're told Geragos called Probation Sunday morning -- hours after the arrest -- to inform them of what went down.
Sources familiar with the situation tell TMZ ... Probation officials have been in contact with D.C. authorities. Probation investigators will conduct their own investigation, and determine if there's good reason to believe Brown committed a crime when he allegedly punched a man in the nose Sunday morning.
The Probation Dept. will submit its report to the judge in the Rihanna case, who will decide if Brown's probation should be revoked. Worst case scenario for Brown -- 4 years in prison for a probation violation.