Law enforcement sources tell TMZ there wasn’t any call about an incident -- we're told cops just happened to roll up on YG after he drove over a curb and was standing outside his car early Tuesday morning.

TMZ has also obtained a photo from the scene, which appears to show YG sitting on the curb with his head resting on his arms, just a few feet away from his car as a police officer stands in front of him.

We're told it wasn’t clear if YG was under the influence of drugs or alcohol. Our sources say officers did not administer a breathalyzer test, but cops did take a blood sample. He was subsequently booked for a misdemeanor DUI.