T.I. Arrest -- Probation Violation Probe Underway

9/2/2010 6:20 PM PDT

TI Arrested -- Probation Violation Probe Underway

TMZ has learned ... federal officials are "in the process" of determining if they will try to revoke T.I.'s probation in the wake of his arrest late last night.

As we first reported, T.I. -- who is still on probation for illegally possessing machine guns a few years ago --  was arrested again last night for possession of a controlled substance on the Sunset Strip.

Now, United States Attorney Sally Quillian Yates tells us, "The probation office is in the process of determining what happened and will make a recommendation regarding Mr. Harris when they have all the facts."

If officials determine T.I. did violate his probation, he could be sent back to the slammer to serve some serious prison time.

UPDATE: We're told T.I.'s probation officer has asked the rapper to return to Atlanta.