Child Services Launch Investigation into Chris Brown On Heels of Gun Arrest

3:25 PM PT -- Chris refused to speak with investigators. In fact, we're told he wouldn't even let LAPD or the DCFS rep enter his security gate.

Chris Brown's getting a visit from police and child services as part of the investigation into the alleged gun incident at his house ... TMZ has learned.

Law enforcement sources tell us DCFS went to Chris' house Thursday afternoon to check on his daughter Royalty's well-being. We're told the 2-year-old is at the house right now. LAPD is accompanying the DCFS investigator.

Our sources connected to Chris tell us they believe Nia Guzman -- Royalty's mother -- filed a complaint against him after Baylee Curran claimed Brown pulled a gun on her.

Chris was booked for assault with a deadly weapon. The D.A. has yet to file any charges against him.