TMZ broke the story ... Underwood was arrested earlier this month outside his Cloud 9 hookah lounge in Port St. Lucie for violating his probation -- a misdemeanor in Florida. The lounge is co-owned by Underwood.

According to law enforcement, a warrant was issued for Underwood's arrest after his probation officer discovered Underwood had failed a drug test. The probation officer listed other violations as well, like failing to complete a substance abuse program.

Underwood is currently on probation stemming from his prior arrest in April ... when cops say he was in possession of marijuana.