11:52 AM PT -- Polo G's attorney, Bradford Cohen, tells us, "Polo is being held under the guise that the police department needs to double check that he is not a convicted felon as there was a purported firearm found in the home. He is not and never was a convicted felon. Any previous charges he had I got dismissed and it's all public record. They are also denying myself and my California law partner Zoe Aron access to him while he is being illegally detained."
11:50 AM PT -- A law enforcement source tells us the warrant has to do with Polo G's brother, Taurean (known as Trench Baby) ... we're told Polo was detained because officers are trying to determine if he was harboring a fugitive.
For his part, Trench Baby posted about the raid happening, and his message doesn't seem too positive.
Polo G's house is currently swarmed by law enforcement, and the rapper's in handcuffs.
Officers from the Los Angeles Police Department hit Polo's L.A.-area home early Wednesday with a search warrant. In video from the scene -- obtained by TMZ Hip Hop -- you can see a ton of law enforcement vehicles lined up on Polo's street.