"Celebrity Rehab" star Frankie Lons -- the mother of singer Keyshia Cole -- is back in jail this morning ... after cops say they found her in possession of "drug-related material"
Law enforcement tells us ... cops stopped Frankie for a routine traffic violation yesterday when they noticed an active warrant out for her arrest stemming from a probation violation.
We're told cops then performed a search -- and found "drug-related material" on her person.
Lons was arrested and transported to a nearby jail -- where she was booked for the probation violation and misdemeanor possession of drug-related material.
This morning, Lons is still in custody.