Alexander Ludwig -- Underage 'Hunger Games' Star Leaves Hollywood Bar Undercover

11:50 AM PT: We're told the California Dept. of Alcoholic Beverage Control has just opened an investigation into The Sayers Club over the Ludwig photos. A rep for the ABC tells TMZ, "We're looking into it."

"Hunger Games" star Alexander Ludwig blew off some steam Tuesday night by kicking back at The Sayers Club in Hollywood -- problem is, he's 19 and the club cannot legally allow anyone in who is under 21.

The pic on the left shows Alexander at an event earlier in the evening. Then we got more pics -- shot at around 11:45 PM -- showing Alexander, wearing the same leather jacket and skinny jeans -- covering his face leaving Sayers.

The California Dept. of Alcoholic Beverage Control tells TMZ ... Sayers has a Type 48 license, meaning only patrons 21 and over can enter.

Robbie McKay, Director of Communications for Sayers, tells TMZ when security spotted Ludwig inside the club he was asked to leave.