Justin Bieber -- More Weed. More Problems.

Justin Bieber's at the center of ANOTHER marijuana controversy -- TMZ has learned MORE photos of the singer holding a blunt were being shopped to media outlets.

The photos -- which we've seen -- show 18-year-old Justin and his bud Lil Za casually passing the weed-filled stogie back and forth while hanging outside of an L.A. home.

FYI -- Lil Za is the guy who was pulled over and detained for driving Bieber's Ferrari without a license early Friday morning. We're told the marijuana photos were taken Thursday.

It's not the first time Bieber's been photographed with grass ... just last month, Justin was pictured with another rapper -- Lil Twist -- holding a smoldering joint at a hotel party in Newport Beach. Ironically, Bieber loaned the same Ferrari to Lil Twist January 1st. You'll recall a photog was struck and killed by another motorist while shooting pics of Twist being pulled over for speeding.

We reached out to Justin's camp for comment ... about smoking pot and loaning his car to less-than-responsible people. So far no word back.