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Justin Bieber has made a fortune by sticking close to his wholesome heartthrob image, but lately that image is being threatened by two online photos that show him holding a suspicious cigarette and sharing a bubbly drink with his pal Lil Twist.

Now some Bieber fans are questioning whether the 19-year-old Dallas rapper is a bad influence on the singer.

On Saturday, Bieber, 18, seemed to be expressing contrition for the alleged pot-smoking photos that were posted Friday on TMZ, tweeting, "i never want to let any of you down. i love u."

Bieber's rep declined to comment on Bieber's latest troubles.

TMZ claimed the pictures were taken Jan. 2 at a party in a Newport Beach, Calif., hotel room. In the images, Bieber is seen laughing and chatting with other party goers while holding what looks like a blunt - a hollowed out cigar packed with pot - between his fingers.

TMZ reported that Bieber's pal, Lil Twist, was also at the party and that he and his brother were the ones rolling the blunts.

A spokesman for Lil Twist did not respond immediately to ABCNews.com's request for comment.

Writing on Twitter Saturday, Bieber didn't address the situation directly but appeared to refer obliquely to his behavior. "i see all of u. i hear all of u. i never want to let any of you down. i love u. and..thank u," he wrote.

Fans responding to the tweet reassured Bieber that he'd never let them down, with one writing, "Weed doesn't end the world."

But earlier, when he'd tweeted, "everyday growing and learning. trying to be better," one follower snarked, "learning how to roll more blunts?"

This isn't the first time fans have questioned the friendship between Lil Twist and Bieber.

@liltwist/Instagram

On Jan. 1, the rapper posted a photo on Facebook and Twitter of himself, standing next to Bieber while pouring a bubbly drink into two glasses.

Response ranged from "I hate you! You give bad influence to @justinbieber ! Just stay away from him," from one fan, to "Justin is all grown up he knows what's right and what's wrong, it's annoying u guys hating everyone that touches Justin!" from a self-described "belieber."

Twist is also at the center of the recent incident in which paparazzo Chris Guerra, 29, was killed New Year's Day while trying to photograph Bieber's white Ferrari. The rapper was behind the wheel at the time.

Lil Twist and Bieber have been friends for a couple years. In 2010, Bieber told MTV News, "Lil Twist is my homey and we're working on stuff for fun."

But Twist, who is signed to hip hop superstar Lil Wayne's label Young Money, has yet to release a full studio album.

Instead, he seems to be enjoying the life of a rap star, plastering his Twitter page with the words "Sex, Drugs & Rock 'n Roll" and profile photo that shows him exhaling a cloud of smoke and posting pictures of him and Bieber posing next to a private jet and vacationing in a tropical locale.