Keshia Cole’s mother Frankie is back in jail again.

“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” … TMZ has learned.

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.